clang-format -i *.cc *.c *.h

.clang-format

@@ -0,0 +1,9 @@
+---
+Language:        Cpp
+BasedOnStyle:  LLVM
+ConstructorInitializerIndentWidth: 8
+ContinuationIndentWidth: 8
+IndentWidth:     4
+InsertNewlineAtEOF: true
+PointerAlignment: Left
+SpacesBeforeTrailingComments: 2

.gitignore

@@ -1,3 +1,5 @@
 *.bin
+*.o
+*.elf
+*.com
 polos.img
-polmon.com

Makefile

@@ -1,7 +1,7 @@
 dev-image = 5150-dev
 
 %.bin: %.asm
-	nasm $? -o $@
+	nasm $< -o $@
 
 crc16.s: crc16.c
 	ia16-elf-gcc -S -Os -o crc16.s crc16.c
@@ -19,23 +19,23 @@ LDFLAGS = -mregparmcall -Wl,--gc-sections -Os -nostdlib -flto
 %.elf:
 	$(LD) $(LDFLAGS) $(CPPFLAGS) -o $@ $^
 
-bootsectors = fat12boot.bin wozmon.bin
+%.com: %.elf
+	ia16-elf-objcopy -O binary $< $@
 
+bootsectors = fat12boot.bin wozmon.bin
 $(bootsectors):
-	ia16-elf-objcopy -O binary $? $@
-	truncate -s 510 $@
-	printf "\125\252" >> $@
+	ia16-elf-objcopy -O binary $< $@
 
 fat12boot.elf: fat12boot.o fat12.o bootsect.S
 fat12boot.elf: LDFLAGS += -T bootsect.ld
 
 fat12boot.bin: fat12boot.elf
 
-polmon.elf: LDFLAGS += -T flat0600.ld
-polmon.elf: polmon.o
+polmon.elf: LDFLAGS += -T flat1000.ld
+polmon.elf: polmon.o stdlib.o
 
-polmon.com: polmon.elf
-	ia16-elf-objcopy -O binary $? $@
+polio.elf: LDFLAGS += -T flat0600.ld
+polio.elf: polio.s fat12.o
 
 wozmon.o: polmon.cc
 wozmon.o: CPPFLAGS = -DWOZMON=1
@@ -48,15 +48,20 @@ wozmon.elf: CPPFLAGS += -DNOBPB
 
 wozmon.bin: wozmon.elf
 
-polos.img: fat12boot.bin polmon.com
+paracli.elf: LDFLAGS += -T doscom.ld
+paracli.elf: paracli.s paracomm.o
+
+polos.img: fat12boot.bin polmon.com polio.com paracli.com
 	dd if=/dev/zero of=$@ bs=512 count=720
 	mformat -i $@ -t 40 -h 2 -s 9
-	mcopy -i $@ polmon.com ::/polmon.com
+	mcopy -i $@ polio.com ::/
+	mcopy -i $@ polmon.com ::/
+	mcopy -i $@ paracli.com ::/
 	dd if=fat12boot.bin of=$@ conv=notrunc
 
 .PHONY: clean
 clean:			## Remove generated files
-	rm -rf *.bin polmon.com polos.img
+	rm -rf *.bin *.elf *.o *.com polos.img
 
 .PHONY: dev-image
 dev-image:
@@ -68,7 +73,7 @@ dev: dev-image	## Launch a dev container
 
 
 .PHONY: binaries
-binaries:		## Build all binaries
+binaries:		## Build all small binaries
 	docker build --build-arg TARGET=readfloppy.bin -o . --target=export .
 	docker build --build-arg TARGET=writefloppy.bin -o . --target=export .
 	docker build --build-arg TARGET=crc16.bin -o . --target=export .
@@ -76,11 +81,9 @@ binaries:		## Build all binaries
 	docker build --build-arg TARGET=hello.bin -o . --target=export .
 	docker build --build-arg TARGET=copy.bin -o . --target=export .
 	docker build --build-arg TARGET=call.bin -o . --target=export .
-	docker build --build-arg TARGET=debug.bin -o . --target=export .
-	docker build --build-arg TARGET=dosdbt.bin -o . --target=export .
 	docker build --build-arg TARGET=format.bin -o . --target=export .
-	docker build --build-arg TARGET=polmon.com -o . --target=export .
-	docker build --build-arg TARGET=fat12boot.bin -o . --target=export .
+	docker build --build-arg TARGET=readio.bin -o . --target=export .
+	docker build --build-arg TARGET=writeio.bin -o . --target=export .
 
 .PHONY: floppy
 floppy:			## Make a bootable floppy image

arduino/kbd/kbd.cc

@@ -0,0 +1,193 @@
+// keyboard wiring diagram:
+// https://www.minuszerodegrees.net/5150/misc/5150_keyboard_reset.jpg
+
+#include "Arduino.h"
+
+constexpr int kClockPin = PC6;
+constexpr int kDataPin = PC4;
+
+constexpr int kBitDelayMicros = 100;
+constexpr int kCodeDelayMicros = 200;
+constexpr int kKeyDelayMicros = 100;
+
+namespace {
+
+void sendCode(int code) {
+    // preconditions: clock and data pins are INPUT
+
+    while (digitalRead(kDataPin) == LOW || digitalRead(kClockPin) == LOW) {
+        // wait. we're not allowed to send
+    }
+
+    digitalWrite(kDataPin, LOW);
+    digitalWrite(kClockPin, LOW);
+
+    pinMode(kClockPin, OUTPUT);
+    delayMicroseconds(kBitDelayMicros);
+    pinMode(kClockPin, INPUT);
+    // delayMicroseconds(kDelayMicros);
+
+    for (int i = 0; i < 8; i++) {
+        if ((code & (1 << i)) == 0) {
+            // send a 0
+            pinMode(kDataPin, OUTPUT);
+        } // else do nothing, it's already a 1
+        delayMicroseconds(kBitDelayMicros);
+
+        pinMode(kClockPin, OUTPUT);
+        delayMicroseconds(kBitDelayMicros);
+        pinMode(kDataPin, INPUT);
+        pinMode(kClockPin, INPUT);
+    }
+    delayMicroseconds(kCodeDelayMicros);
+}
+
+enum State {
+    kReady,
+    kMaybeReset,
+};
+
+constexpr int kResetDelay = 19;
+
+constexpr int kLetterCodes[] = {
+        0x1E, // 'a'
+        0x30, 0x2E, 0x20, 0x12, 0x21, 0x22, 0x23, 0x17, 0x24,
+        0x25, 0x26, 0x32, 0x31, 0x18, 0x19, 0x10, 0x13, 0x1F,
+        0x14, 0x16, 0x2F, 0x11, 0x2D, 0x15, 0x2c,
+};
+
+constexpr int kNumberCodes[] = {
+        0x0B, // '0'
+        0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A,
+};
+
+void sendNormalCode(int code) {
+    sendCode(code);
+    sendCode(code | 0x80);
+}
+
+void sendShiftCode(int code) {
+    sendCode(42); // left shift
+    sendNormalCode(code);
+    sendCode(42 | 0x80);
+}
+
+void sendCtrlAltDel() {
+    sendCode(0x1d); // ctrl
+    sendCode(0x38); // alt
+    sendCode(0x53); // del
+    sendCode(0x53 | 0x80);
+    sendCode(0x38 | 0x80);
+    sendCode(0x1d | 0x80);
+}
+
+void sendCtrlBreak() {
+    sendCode(0x1d); // ctrl
+    sendCode(0x46); // break
+    sendCode(0x46 | 0x80);
+    sendCode(0x1d | 0x80);
+}
+
+} // namespace
+
+void sendAsciiChar(int c) {
+    if (c >= 'a' && c <= 'z') {
+        return sendNormalCode(kLetterCodes[c - 'a']);
+    } else if (c >= '0' && c <= '9') {
+        return sendNormalCode(kNumberCodes[c - '0']);
+    } else if (c >= 'A' && c <= 'Z') {
+        return sendShiftCode(kLetterCodes[c - 'A']);
+    }
+    switch (c) {
+    case '-':
+        return sendNormalCode(12);
+    case '=':
+        return sendNormalCode(13);
+    case '[':
+        return sendNormalCode(26);
+    case ']':
+        return sendNormalCode(27);
+    case ';':
+        return sendNormalCode(39);
+    case '\'':
+        return sendNormalCode(40);
+    case ',':
+        return sendNormalCode(51);
+    case '.':
+        return sendNormalCode(52);
+    case '/':
+        return sendNormalCode(53);
+    case ' ':
+        return sendNormalCode(57);
+    case '\n':
+        return sendNormalCode(28);
+
+    case '!':
+        return sendShiftCode(2);
+    case '@':
+        return sendShiftCode(3);
+    case '#':
+        return sendShiftCode(4);
+    case '$':
+        return sendShiftCode(5);
+    case '%':
+        return sendShiftCode(6);
+    case '^':
+        return sendShiftCode(7);
+    case '&':
+        return sendShiftCode(8);
+    case '*':
+        return sendShiftCode(9);
+    case '(':
+        return sendShiftCode(10);
+    case ')':
+        return sendShiftCode(11);
+    case '_':
+        return sendShiftCode(12);
+    case '+':
+        return sendShiftCode(13);
+
+    case '{':
+        return sendShiftCode(26);
+    case '}':
+        return sendShiftCode(27);
+    case ':':
+        return sendShiftCode(39);
+    case '"':
+        return sendShiftCode(40);
+    case '<':
+        return sendShiftCode(51);
+    case '>':
+        return sendShiftCode(52);
+    case '?':
+        return sendShiftCode(53);
+
+    case 0:
+        return sendCtrlAltDel();
+    case 27:
+        return sendCtrlBreak(); // escape
+    }
+}
+
+void setupKbd() {
+    pinMode(kClockPin, INPUT);
+    pinMode(kDataPin, INPUT);
+}
+
+void checkKbdReset() {
+    static State state = kReady;
+    static int lastclocklow = 0;
+
+    int clockp = digitalRead(kClockPin);
+    if (state == State::kReady && clockp == LOW) {
+        state = State::kMaybeReset;
+        lastclocklow = millis();
+    } else if (state == State::kMaybeReset) {
+        if (clockp == HIGH && millis() - lastclocklow > kResetDelay) {
+            delay(1);
+            state = State::kReady;
+            sendCode(0xaa);
+            Serial.println("Reset!");
+        }
+    }
+}

arduino/kbd/kbd.h

@@ -0,0 +1,5 @@
+#pragma once
+
+void sendAsciiChar(int c);
+void setupKbd();
+void checkKbdReset();

arduino/kbd/kbd.ino

@@ -1,213 +1,67 @@
-// keyboard wiring diagram: https://www.minuszerodegrees.net/5150/misc/5150_keyboard_reset.jpg
+#include "kbd.h"
+#include "paracomm.h"
+#include "parallel.h"
 
-constexpr int kClockPin = PC6;
-constexpr int kDataPin = PC4;
-
-constexpr int kBitDelayMicros = 100;
-constexpr int kCodeDelayMicros = 200;
-constexpr int kKeyDelayMicros = 100;
+ParaComms pc;
 
 void setup() {
-  // put your setup code here, to run once:
-  Serial.begin(115200);
-  pinMode(LED_BUILTIN, OUTPUT);
+    // put your setup code here, to run once:
+    Serial.begin(115200);
+    pinMode(LED_BUILTIN, OUTPUT);
 
-  pinMode(kClockPin, INPUT);
-  pinMode(kDataPin, INPUT);
+    setupKbd();
+    setupParallel();
 
-  Serial.println("kbd 0.1");
-}
+    pc = ParaComms{
+            .mosi_cb =
+                    [](uint8_t *data, uint8_t len) {
+                        for (int i = 0; i < len; i++) {
+                            Serial.printf("%c", data[i]);
+                            pc.SendByte(data[i]); // echo
+                            if (data[i] == '\r') {
+                                pc.SendByte('\n');
+                            }
+                        }
+                    },
+    };
 
-// 0. reset
-// 0.0. clock line will be held low externally for 20 ms
-//      when back up, keyboard needs to clock 0xAA as a response
-//
-// 1. operation
-// 1.0. just directly clock out scan codes of pressed keys
-
-void sendCode(int code) {
-  Serial.printf("sending code 0x%02x\n", code);
-  // preconditions: clock and data pins are INPUT
-
-  while (digitalRead(kDataPin) == LOW || digitalRead(kClockPin) == LOW) {
-    // wait. we're not allowed to send
-  }
-
-  digitalWrite(kDataPin, LOW);
-  digitalWrite(kClockPin, LOW);
-
-  pinMode(kClockPin, OUTPUT);
-  delayMicroseconds(kBitDelayMicros);
-  pinMode(kClockPin, INPUT);
- // delayMicroseconds(kDelayMicros);
-
-  for (int i = 0; i < 8; i++) {
-    if ((code & (1 << i)) == 0) {
-      // send a 0
-      pinMode(kDataPin, OUTPUT);
-    }  // else do nothing, it's already a 1
-    delayMicroseconds(kBitDelayMicros);
-
-    pinMode(kClockPin, OUTPUT);
-    delayMicroseconds(kBitDelayMicros);
-    pinMode(kDataPin, INPUT);
-    pinMode(kClockPin, INPUT);
-  }
-  delayMicroseconds(kCodeDelayMicros);
-}
-
-enum State {
-  kReady,
-  kMaybeReset,
-};
-
-constexpr int kResetDelay = 19;
-
-State state = State::kReady;
-int lastclocklow = 0;
-
-constexpr int kLetterCodes[] = {
-  0x1E,  // 'a'
-  0x30,
-  0x2E,
-  0x20,
-  0x12,
-  0x21,
-  0x22,
-  0x23,
-  0x17,
-  0x24,
-  0x25,
-  0x26,
-  0x32,
-  0x31,
-  0x18,
-  0x19,
-  0x10,
-  0x13,
-  0x1F,
-  0x14,
-  0x16,
-  0x2F,
-  0x11,
-  0x2D,
-  0x15,
-  0x2c,
-};
-
-constexpr int kNumberCodes[] = {
-  0x0B,  // '0'
-  0x02,
-  0x03,
-  0x04,
-  0x05,
-  0x06,
-  0x07,
-  0x08,
-  0x09,
-  0x0A,
-};
-
-void sendNormalCode(int code) {
-  sendCode(code);
-  sendCode(code | 0x80);
-}
-
-void sendShiftCode(int code) {
-  sendCode(42); // left shift
-  sendNormalCode(code);
-  sendCode(42 | 0x80);
-}
-
-void sendCtrlAltDel() {
-  sendCode(0x1d);  // ctrl
-  sendCode(0x38);  // alt
-  sendCode(0x53);  // del
-  sendCode(0x53 | 0x80);
-  sendCode(0x38 | 0x80);
-  sendCode(0x1d | 0x80);
-}
-
-void sendCtrlBreak() {
-  sendCode(0x1d);  // ctrl
-  sendCode(0x46);  // break
-  sendCode(0x46 | 0x80);
-  sendCode(0x1d | 0x80);
-}
-
-void sendAsciiChar(int c) {
-  if (c >= 'a' && c <= 'z') {
-    return sendNormalCode(kLetterCodes[c - 'a']);
-  } else if (c >= '0' && c <= '9') {
-    return sendNormalCode(kNumberCodes[c - '0']);
-  } else if (c >= 'A' && c <= 'Z') {
-    return sendShiftCode(kLetterCodes[c - 'A']);
-  }
-  switch (c) {
-    case '-': return sendNormalCode(12);
-    case '=': return sendNormalCode(13);
-    case '[': return sendNormalCode(26);
-    case ']': return sendNormalCode(27);
-    case ';': return sendNormalCode(39);
-    case '\'': return sendNormalCode(40);
-    case ',': return sendNormalCode(51);
-    case '.': return sendNormalCode(52);
-    case '/': return sendNormalCode(53);
-    case ' ': return sendNormalCode(57);
-    case '\n': return sendNormalCode(28);
-
-    case '!': return sendShiftCode(2);
-    case '@': return sendShiftCode(3);
-    case '#': return sendShiftCode(4);
-    case '$': return sendShiftCode(5);
-    case '%': return sendShiftCode(6);
-    case '^': return sendShiftCode(7);
-    case '&': return sendShiftCode(8);
-    case '*': return sendShiftCode(9);
-    case '(': return sendShiftCode(10);
-    case ')': return sendShiftCode(11);
-    case '_': return sendShiftCode(12);
-    case '+': return sendShiftCode(13);
-
-    case '{': return sendShiftCode(26);
-    case '}': return sendShiftCode(27);
-    case ':': return sendShiftCode(39);
-    case '"': return sendShiftCode(40);
-    case '<': return sendShiftCode(51);
-    case '>': return sendShiftCode(52);
-    case '?': return sendShiftCode(53);
-
-    case 0: return sendCtrlAltDel();
-    case 27: return sendCtrlBreak();  // escape
-  }
+    Serial.println("kbd 0.1");
 }
 
 void loop() {
-  static int led_counter = 0;
-  static int led = HIGH;
-  if (led_counter > 400000) {
-    led_counter = 0;
-    led = (led == HIGH) ? LOW : HIGH;
-    digitalWrite(LED_BUILTIN, led);
-  }
-  led_counter += 1;
+    static int led_counter = 0;
+    static int led = HIGH;
 
-  int clockp = digitalRead(kClockPin);
-  if (state == State::kReady && clockp == LOW) {
-    state = State::kMaybeReset;
-    lastclocklow = millis();
-  } else if (state == State::kMaybeReset) {
-    if (clockp == HIGH && millis() - lastclocklow > kResetDelay) {
-      delay(1);
-      state = State::kReady;
-      sendCode(0xaa);
-      Serial.println("Reset!");
+    static int mode = 0; // 0 = keyboard, 1 = parallel
+
+    if (led_counter > 400000) {
+        led_counter = 0;
+        led = (led == HIGH) ? LOW : HIGH;
+        digitalWrite(LED_BUILTIN, led);
     }
-  }
+    led_counter += 1;
 
-  if (Serial.available() > 0) {
-    int c = Serial.read();
-    sendAsciiChar(c);
-    //delayMicroseconds(kKeyDelayMicros);
-  }
+    checkKbdReset();
+
+    uint8_t mosib;
+    if (strobeOccurred(mosib)) {
+        pc.FeedMosiData(mosib);
+        uint8_t misob = pc.NextMisoNibble();
+        writeParallel(misob);
+    }
+
+    if (Serial.available() > 0) {
+        int c = Serial.read();
+        if (c == 2) {
+            mode = 0;
+        } else if (c == 3) {
+            mode = 1;
+        } else {
+            if (mode == 0) {
+                sendAsciiChar(c);
+            } else {
+                pc.SendByte(c);
+            }
+        }
+    }
 }

arduino/kbd/paracomm.h

@@ -0,0 +1,124 @@
+#pragma once
+
+#include <stdint.h>
+
+struct ParaComms {
+    using MessageCallback = void (*)(uint8_t *, uint8_t);
+    enum State {
+        kIdle,
+        kLength,
+        kLength2, // for miso
+        kData,
+        // kCrc,  // ?
+    };
+    static constexpr uint8_t kMosiStartByte = 0x42;
+    static constexpr uint8_t kIdleByte = 0x00;
+    static constexpr uint8_t kMisoStartNibble = 0xa;
+    static constexpr uint8_t kMisoIdleNibble = 0x0;
+
+    MessageCallback mosi_cb = nullptr;
+    uint8_t *miso_buffer = nullptr;
+    uint8_t miso_size = 0;
+    uint8_t miso_nibbles_sent = 0;
+    State miso_state = kIdle;
+
+    // double work buffer. one being sent, one being written to
+    uint8_t miso_workbuf[2][256];
+    uint8_t miso_workbuf_idx = 0;
+    uint8_t miso_workbuf_size = 0;
+
+    uint8_t mosi_buffer[256];
+    uint8_t mosi_size = 0;
+    uint8_t mosi_received = 0;
+    State mosi_state = kIdle;
+
+    void SwapBuffers() {
+        miso_buffer = miso_workbuf[miso_workbuf_idx];
+        miso_size = miso_workbuf_size;
+
+        miso_workbuf_idx = (miso_workbuf_idx + 1) % 2;
+        miso_workbuf_size = 0;
+    }
+
+    int SendByte(uint8_t b) {
+        if (miso_workbuf_size == 256) {
+            return -1; // sorry we're full
+        }
+
+        uint8_t *buff = miso_workbuf[miso_workbuf_idx];
+        buff[miso_workbuf_size] = b;
+        miso_workbuf_size += 1;
+
+        return 0;
+    }
+
+    void FeedMosiData(uint8_t b) {
+        switch (mosi_state) {
+        case kIdle:
+            // check start byte
+            if (b == kMosiStartByte) {
+                mosi_state = kLength;
+            } else if (b == kIdleByte) {
+                // just twiddling our thumb drives
+            } else {
+                // Serial.printf("sp: %02x\n", b);
+            }
+            break;
+        case kLength:
+            // assert(b > 0)
+            mosi_size = b;
+            mosi_received = 0;
+            mosi_state = kData;
+            break;
+        case kData:
+            mosi_buffer[mosi_received] = b;
+            mosi_received += 1;
+
+            if (mosi_received == mosi_size) {
+                if (mosi_cb != nullptr) {
+                    mosi_cb(mosi_buffer, mosi_received);
+                }
+                mosi_state = kIdle;
+            }
+        case kLength2: // error
+            return;
+        }
+    }
+
+    uint8_t NextMisoNibble() {
+        switch (miso_state) {
+        case kIdle:
+            if (miso_size == 0) {
+                SwapBuffers();
+                if (miso_size == 0) {
+                    return kMisoIdleNibble;
+                }
+            }
+            miso_state = kLength;
+            return kMisoStartNibble;
+        case kLength:
+            // assert(miso_size > 0);
+            miso_state = kLength2;
+            return miso_size & 0xf;
+        case kLength2:
+            miso_nibbles_sent = 0;
+            miso_state = kData;
+            return miso_size >> 4;
+        case kData: {
+            uint8_t b = miso_buffer[miso_nibbles_sent / 2];
+            if (miso_nibbles_sent % 2 == 0) {
+                b &= 0xf;
+            } else {
+                b >>= 4;
+            }
+            miso_nibbles_sent += 1;
+            if (miso_nibbles_sent == miso_size * 2) {
+                SwapBuffers();
+                miso_state = kIdle;
+            }
+            return b;
+        }
+        }
+        __builtin_unreachable();
+    }
+};

arduino/kbd/parallel.cc

@@ -0,0 +1,95 @@
+#include "parallel.h"
+
+#include <stdint.h>
+
+#include "Arduino.h"
+
+namespace {
+
+constexpr int kParallelDataPins[] = {
+        D9, D8, D7, D6, D5, D4, D3, D2,
+};
+
+constexpr int kParallelBusyPin = D14;
+constexpr int kParallelAckPin = D15;
+constexpr int kParallelPaperoutPin = D12;
+constexpr int kParallelSelectPin = D11;
+
+constexpr int kParallelNibblePins[] = {
+        kParallelSelectPin,
+        kParallelPaperoutPin,
+        kParallelAckPin,
+        kParallelBusyPin,
+};
+
+constexpr bool kParallelNibbleInverted[] = {
+        false,
+        false,
+        false,
+        true,
+};
+
+constexpr int kParallelStrobePin = D10;
+
+volatile bool strobe_pending = false;
+volatile uint8_t strobe_byte = 0;
+
+void strobeIsr() {
+    strobe_pending = true;
+    strobe_byte = readParallel();
+}
+
+} // namespace
+
+uint8_t readParallel() {
+    uint8_t out = 0;
+    for (int i = 0; i < 8; i++) {
+        if (digitalReadFast(digitalPinToPinName(kParallelDataPins[i])) ==
+            HIGH) {
+            out |= (1 << i);
+        }
+    }
+    if (digitalReadFast(digitalPinToPinName(kParallelStrobePin)) == HIGH) {
+        out |= (1 << 8);
+    }
+    return out;
+}
+
+#define BIT(x, n) ((x & (1 << n)) ? HIGH : LOW)
+
+void writeParallel(uint8_t nibble) {
+    for (int i = 0; i < 4; i++) {
+        int lvl = BIT(nibble, i);
+        if (kParallelNibbleInverted[i]) {
+            lvl = lvl == HIGH ? LOW : HIGH;
+        }
+        digitalWriteFast(digitalPinToPinName(kParallelNibblePins[i]), lvl);
+    }
+}
+
+bool strobeOccurred(uint8_t &byte) {
+    bool pending;
+    {
+        noInterrupts();
+        pending = strobe_pending;
+        byte = strobe_byte;
+        strobe_pending = false;
+        interrupts();
+    }
+
+    return pending;
+}
+
+void setupParallel() {
+    for (int i = 0; i < sizeof(kParallelDataPins) / sizeof(int); i++) {
+        pinMode(kParallelDataPins[i], INPUT);
+    }
+    for (int i = 0; i < sizeof(kParallelNibblePins) / sizeof(int); i++) {
+        pinMode(kParallelNibblePins[i], OUTPUT);
+        digitalWrite(kParallelNibblePins[i], HIGH);
+    }
+    pinMode(kParallelStrobePin, INPUT);
+
+    attachInterrupt(digitalPinToInterrupt(kParallelStrobePin), strobeIsr,
+                    FALLING);
+}

arduino/kbd/parallel.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdint.h>
+
+/** Returns the byte present on D0~D7 */
+uint8_t readParallel();
+
+/** Writes a nibble on status pins */
+void writeParallel(uint8_t nibble);
+
+void setupParallel();
+
+/** Returns true and sets the byte if a strobe was received */
+bool strobeOccurred(uint8_t &byte);

bootsect.ld

@@ -17,4 +17,9 @@ SECTIONS {
     .data : {
         *(.data)
     }
+
+    . = 0x7dfe;
+    .magic : {
+        SHORT(0xAA55);
+    }
 }

copy.asm

@@ -11,9 +11,12 @@ main:
     mov si, [si]
     push ds
     push es
-    pop ds
+    mov ax, cs
+    mov ds, ax
+    mov es, ax
     cld
     rep movsw
+    pop es
     pop ds
 
     retf 6

crc16.c

@@ -1,6 +1,6 @@
 #include <stdint.h>
 
-#define kDataAddr ((uint8_t*) 0x0000)
+#define kDataAddr ((uint8_t*)0x0000)
 
 uint16_t crc16(int data_len) {
     const uint8_t* data = kDataAddr;
@@ -19,17 +19,15 @@ uint16_t crc16(int data_len) {
     return crc;
 }
 
-asm (
-        ".global main      \n"
-        "main:             \n"
-        "  push %bp        \n"
-        "  mov %sp, %bp    \n"
-        "  mov 8(%bp), %si \n"
-        "  push (%si)      \n"
-        "  call crc16      \n"
-        "  add $0x2, %sp   \n"
-        "  mov 6(%bp), %di \n"
-        "  mov %ax, (%di)  \n"
-        "  pop %bp         \n"
-        "  lret $4         \n"
-        );
+asm(".global main      \n"
+    "main:             \n"
+    "  push %bp        \n"
+    "  mov %sp, %bp    \n"
+    "  mov 8(%bp), %si \n"
+    "  push (%si)      \n"
+    "  call crc16      \n"
+    "  add $0x2, %sp   \n"
+    "  mov 6(%bp), %di \n"
+    "  mov %ax, (%di)  \n"
+    "  pop %bp         \n"
+    "  lret $4         \n");

crt0.c

@@ -3,24 +3,22 @@
 
 int main();
 
-asm (
-        ".section .init     \n"
-        ".global _start     \n"
-        "_start:            \n\t"
-        "mov %cs, %ax       \n\t"
-        "mov %ax, %ds       \n\t"
-        "mov %ax, %es       \n\t"
-        "cli                \n\t"
-        "mov %ax, %ss       \n\t"
-        "mov $0x1000, %ax   \n\t"
-        "mov %ax, %sp       \n\t"
-        "sti                \n\t"
-        "jmp main"
-);
+asm(".section .init     \n"
+    ".global _start     \n"
+    "_start:            \n\t"
+    "mov %cs, %ax       \n\t"
+    "mov %ax, %ds       \n\t"
+    "mov %ax, %es       \n\t"
+    "cli                \n\t"
+    "mov %ax, %ss       \n\t"
+    "mov $0x1000, %ax   \n\t"
+    "mov %ax, %sp       \n\t"
+    "sti                \n\t"
+    "jmp main");
 
 void* memset(void* ptr, int val, size_t len) {
     uint8_t* p = ptr;
-    while(len--) {
+    while (len--) {
         *p++ = val;
     }
     return ptr;

doscom.ld

@@ -0,0 +1,20 @@
+SECTIONS {
+    . = 0x100;
+
+    .text : {
+        KEEP(*(.init))
+        *(.text*)
+    }
+
+    .rodata : {
+        *(.rodata*)
+    }
+
+    .bss (NOLOAD) : {
+        * (.bss)
+    }
+
+    .data : {
+        *(.data)
+    }
+}

fat12.c

@@ -6,8 +6,7 @@
 #define kHeads 2
 #define kFatSizeSectors 2
 #define kRootDirSizeSectors 7
-#define kDataRegionStartSector (1 + kFatSizeSectors*2 + kRootDirSizeSectors)
-
+#define kDataRegionStartSector (1 + kFatSizeSectors * 2 + kRootDirSizeSectors)
 
 typedef struct {
     char name[8];
@@ -23,28 +22,25 @@ typedef struct {
 static uint8_t* gFat;
 static direntry* gRootdir;
 
-
 static int readsector(int c, int h, int s, uint8_t* addr) {
-    register uint8_t* dest asm ("bx") = addr;
-    register uint8_t nsects asm ("al") = 1;
-    register uint8_t func asm ("ah") = 0x02;
-    register uint8_t sect asm ("cl") = s;
-    register uint8_t cyl asm ("ch") = c;
-    register uint8_t head asm ("dh") = h;
-    register uint8_t drive asm ("dl") = 0;
-    register uint16_t seg asm ("es") = 0;
+    register uint8_t* dest asm("bx") = addr;
+    register uint8_t nsects asm("al") = 1;
+    register uint8_t func asm("ah") = 0x02;
+    register uint8_t sect asm("cl") = s;
+    register uint8_t cyl asm("ch") = c;
+    register uint8_t head asm("dh") = h;
+    register uint8_t drive asm("dl") = 0;
+    register uint16_t seg asm("es") = 0;
 
     register uint8_t ret asm("ah");
 
     for (int i = 0; i < 3; i++) {
-        asm volatile ("int $0x13"
-                : "=r" (ret)
-                : "r" (dest), "r" (nsects), "r" (func), "r" (sect),
-                  "r" (cyl), "r" (head), "r" (drive), "r" (seg));
-        if (ret == 0x80) {
-            continue;
-        } else {
-            return ret;
+        asm volatile("int $0x13"
+                     : "=r"(ret)
+                     : "r"(dest), "r"(nsects), "r"(func), "r"(sect), "r"(cyl),
+                       "r"(head), "r"(drive), "r"(seg));
+        if (ret != 0x80) {
+            break;
         }
     }
 
@@ -55,20 +51,21 @@ static int readcluster(int cluster) {
     int offs = cluster * 3 / 2;
     if (cluster % 2) {
         // high nibble is lsb + whole byte
-        return ((gFat[offs] & 0xf0) >> 4) + (gFat[offs+1] << 4);
+        return ((gFat[offs] & 0xf0) >> 4) + (gFat[offs + 1] << 4);
     } else {
-        return gFat[offs] + ((gFat[offs+1] & 0x0f) << 8);
+        return gFat[offs] + ((gFat[offs + 1] & 0x0f) << 8);
     }
 }
 
 static void cluster2chs(int cluster, int* c, int* h, int* s) {
-    int logicalsector = kDataRegionStartSector + (cluster - 2) * kSectorsPerCluster;
+    int logicalsector =
+            kDataRegionStartSector + (cluster - 2) * kSectorsPerCluster;
     *s = (logicalsector % kSectorsPerTrack) + 1;
     *h = (logicalsector / kSectorsPerTrack) % kHeads;
     *c = logicalsector / (kHeads * kSectorsPerTrack);
 }
 
-static int strncmp(const char* s1, const char *s2, size_t len) {
+static int strncmp(const char* s1, const char* s2, size_t len) {
     for (int i = 0; i < len && s1[i]; i++) {
         if (s1[i] != s2[i]) {
             return 1;
@@ -80,7 +77,7 @@ static int strncmp(const char* s1, const char *s2, size_t len) {
 
 static int loadfile(direntry* entry, void* addr) {
     int cluster = entry->cluster;
-    for (int i = 0; i < entry->size; i+=1024) {
+    for (int i = 0; i < entry->size; i += 1024) {
         int c, h, s;
         cluster2chs(cluster, &c, &h, &s);
         if (readsector(c, h, s, addr + i)) {

fat12.h

@@ -11,5 +11,5 @@ int fat12_init(void* fat_addr, void* rootdir_addr);
  * Returns:
  *  -4 if file is not found
  *  -5 if there is a disk error
- */ 
+ */
 int fat12_readfile(const char* name, void* addr);

fat12boot.c

@@ -7,15 +7,12 @@
 #define kFatAddress ((void*)0x1000)
 #define kRootDirAddress ((void*)0x1200)
 
-
 static int putchar(int c) {
-    register uint8_t khar asm ("al") = c;
-    register uint8_t func asm ("ah") = 0x0e;
-    register uint8_t page asm ("bh") = 0;
+    register uint8_t khar asm("al") = c;
+    register uint8_t func asm("ah") = 0x0e;
+    register uint8_t page asm("bh") = 0;
 
-    asm volatile ("int $0x10"
-            :: "r" (khar), "r" (func), "r" (page)
-            : "bp");
+    asm volatile("int $0x10" ::"r"(khar), "r"(func), "r"(page) : "bp");
 
     return c;
 }
@@ -27,33 +24,30 @@ static int puts(const char* msg) {
     return 0;
 }
 
-__attribute__((noreturn))
-static void die(const char* msg) {
+__attribute__((noreturn)) static void die(const char* msg) {
     puts(msg);
     while (1) {
     }
     __builtin_unreachable();
 }
 
-__attribute__((noreturn))
-static void jump(void* addr) {
-    asm volatile ("ljmp $0,%0" :: "i"(addr));
+__attribute__((noreturn)) static void jump(void* addr) {
+    asm volatile("ljmp $0,%0" ::"i"(addr));
     __builtin_unreachable();
 }
 
-__attribute__((noreturn))
-static void loadpolmon() {
+__attribute__((noreturn)) static void loadpolmon() {
     if (fat12_init(kFatAddress, kRootDirAddress)) {
         die("fi");
     }
 
-    if (fat12_readfile("POLMON  COM", kPolmonAddress)) {
-        die("pnf");
+    while (fat12_readfile("POLIO   COM", kPolmonAddress)) {
+        asm volatile("mov $00, %%ah      \n\t"
+                     "int $0x16          \n\t" ::
+                             : "ax");
     }
 
     jump(kPolmonAddress);
 }
 
-int main() {
-    loadpolmon();
-}
+int main() { loadpolmon(); }

flat1000.ld

@@ -0,0 +1,20 @@
+SECTIONS {
+    . = 0x1000;
+
+    .text : {
+        KEEP(*(.init))
+        *(.text*)
+    }
+
+    .rodata : {
+        *(.rodata*)
+    }
+
+    .bss (NOLOAD) : {
+        * (.bss)
+    }
+
+    .data : {
+        *(.data)
+    }
+}

paracli.s

@@ -0,0 +1,80 @@
+    .arch i8086,jumps
+    .code16
+    .intel_syntax noprefix
+
+    .section .init
+    .global _start
+_start:
+    mov ax, cs
+    mov ds, ax
+    mov es, ax
+    cli
+    mov ss, ax
+    mov sp, 0x100
+    sti
+    jmp main
+
+    .section .text.parcb
+parcb:
+    push bx
+    push si
+    push bp
+    mov si, ax
+1:
+    test dx, dx
+    jz 0f
+    mov al, [si]
+    mov ah, 0x0e
+    mov bh, 0
+    int 0x10
+    dec dx
+    inc si
+    jmp 1b
+0:
+    pop bp
+    pop si
+    pop bx
+    ret
+
+    .section .rodata.l0
+.l0: .ascii "> "
+.l1: .ascii "."
+
+delay = 500
+
+    .section .text.main
+    .global main
+main:
+    mov ax, 0x0002
+    int 0x10
+    mov ax, offset parcb
+    call paracomm_init
+0:
+    mov ah, 0x01
+    int 0x16
+    jz 1f
+    mov ah, 0x00
+    int 0x16
+    mov ah, 0
+    call paracomm_send
+    test ax, ax
+    jz 0b
+1:
+    call paracomm_nextbyte
+    mov dx, 0x3bc
+    out dx, al
+    add dl, 2
+    mov al, 1
+    out dx, al
+    mov cx, delay
+2:  loop 2b    
+    mov al, 0
+    out dx, al
+    mov cx, delay
+3:  loop 3b    
+    dec dl
+    in al, dx
+    mov cl, 4
+    shr al, cl
+    call paracomm_feed
+    jmp 0b

paracomm.c

@@ -0,0 +1,124 @@
+#include "paracomm.h"
+
+#include <stdlib.h>
+
+#define kMosiIdleByte 0x00
+#define kMosiStartByte 0x42
+#define kMisoIdleNibble 0x0
+#define kMisoStartNibble 0xa
+
+static uint8_t mosi_workbuf[2][256];
+static uint8_t mosi_workbuf_idx;
+static uint8_t mosi_workbuf_size;
+
+static uint8_t* mosi_sendbuf;
+static uint8_t mosi_size;
+static uint8_t mosi_sent;
+
+static uint8_t mosi_state;
+
+static uint8_t miso_recvbuf[256];
+static uint8_t miso_size;
+static uint8_t miso_received_nibbles;
+static uint8_t miso_state;
+static void (*miso_cb)(const uint8_t*, uint8_t);
+
+static void swapbuffers() {
+    mosi_sendbuf = mosi_workbuf[mosi_workbuf_idx];
+    mosi_size = mosi_workbuf_size;
+
+    mosi_workbuf_size = 0;
+    mosi_workbuf_idx = (mosi_workbuf_idx + 1) % 2;
+}
+
+uint8_t paracomm_nextbyte() {
+    switch (mosi_state) {
+    case 0:
+        if (mosi_size == 0) {
+            swapbuffers();
+            if (mosi_size == 0) {
+                return kMosiIdleByte;
+            }
+        }
+        mosi_state = 1;
+        return kMosiStartByte;
+    case 1:
+        // assert(mosi_size > 0)
+        mosi_sent = 0;
+        mosi_state = 2;
+        return mosi_size;
+    case 2: {
+        uint8_t b = mosi_sendbuf[mosi_sent];
+        mosi_sent += 1;
+
+        if (mosi_sent == mosi_size) {
+            swapbuffers();
+            mosi_state = 0;
+        }
+
+        return b;
+    }
+    }
+
+    __builtin_unreachable();
+}
+
+void paracomm_feed(uint8_t n) {
+    switch (miso_state) {
+    case 0:
+        if (n == kMisoStartNibble) {
+            miso_state = 1;
+        } else if (n == kMisoIdleNibble) {
+        } else {
+            // error: spurious nibble
+        }
+        break;
+    case 1:
+        miso_size = n;
+        miso_state = 2;
+        break;
+    case 2:
+        miso_size += n << 4;
+        miso_received_nibbles = 0;
+        miso_state = 3;
+        break;
+    case 3: {
+        uint8_t idx = miso_received_nibbles / 2;
+        if (miso_received_nibbles % 2 == 0) {
+            miso_recvbuf[idx] = n;
+        } else {
+            miso_recvbuf[idx] += n << 4;
+        }
+        miso_received_nibbles += 1;
+
+        if (miso_received_nibbles == 2 * miso_size) {
+            if (miso_cb != 0) {
+                miso_cb(miso_recvbuf, miso_size);
+            }
+            miso_state = 0;
+        }
+    } break;
+    }
+}
+
+void paracomm_init(miso_cb_t cb) {
+    mosi_size = 0;
+    mosi_workbuf_idx = 0;
+    mosi_workbuf_size = 0;
+    mosi_state = 0;
+
+    miso_state = 0;
+    miso_cb = cb;
+}
+
+int paracomm_send(uint8_t b) {
+    if (mosi_workbuf_size == 256) {
+        return -1;
+    }
+
+    uint8_t* buff = mosi_workbuf[mosi_workbuf_idx];
+    buff[mosi_workbuf_size] = b;
+    mosi_workbuf_size += 1;
+
+    return 0;
+}

paracomm.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <stdint.h>
+
+typedef void (*miso_cb_t)(const uint8_t* buff, uint8_t size);
+
+/** Must call first **/
+void paracomm_init(miso_cb_t miso_cb);
+
+/** Sends a single byte.
+ * Returns: 0 if no error, non-0 otherwise.
+ */
+int paracomm_send(uint8_t b);
+
+/** Call after reading a nibble from the port */
+void paracomm_feed(uint8_t n);
+
+/** Yields the next byte to send out the port */
+uint8_t paracomm_nextbyte();

polio.s

@@ -0,0 +1,189 @@
+    .arch i8086,jumps
+    .code16
+    .intel_syntax noprefix
+
+    .section .init
+    .global _start
+_start:
+    jmp main
+
+
+diskpointer = 0x1e*4
+dbtbase = 0x0500
+
+    .section .text.dosdbt
+    .local dosdbt
+dosdbt:                    # assumes es=0
+    push si
+    push di
+    push ds
+    mov si, diskpointer
+    lds si, [si]
+    mov di, dbtbase
+    mov cx, 0x0a           # size of the dbt
+    cld
+    rep movsb              # move dbt to dbtbase
+    pop ds
+    mov al, 9              # sectors per track
+    mov si, dbtbase
+    mov [si+4], al         # set number of sectors
+    mov di, diskpointer
+    mov [di], si           # new int1eh offset
+    mov [di+2], ds         # and segment
+    pop di
+    pop si
+    ret
+
+    .section .text.int80stuff
+
+# near copy [param 2] bytes, es:[param 0] -> es:[param 1]
+copy:
+    mov si, [bp+0]      # source
+    mov di, [bp+2]      # destination
+    mov cx, [bp+4]      # length
+    cld
+    rep movsb
+    ret
+
+## floppy stuff
+
+# same as read but with a different int13h:ah value
+writesector:
+    mov ax, 0x0301      # write command, 1 sector
+    jmp 0f
+
+# params: addr, c, h, s
+# return status in ah, sectors read (1 or 0) in al
+readsector:
+    mov ax, 0x0201      # read command, 1 sector
+0:
+    mov bx, [bp+0]      # addr
+    mov ch, [bp+2]      # c
+    mov dh, [bp+4]      # h
+    mov cl, [bp+6]      # s
+    int 0x13
+    ret
+
+
+# params: c, h
+# returns: status in ah, 0 in al?
+
+buffer = 0xe000         # buffer needs to be big enough for a whole track
+                        # (for some reason), so 9 * 512 bytes = 0x1200 bytes
+sectors = 9
+
+formattrack:
+    mov bx, buffer
+    xor cx, cx
+0:
+    cmp cl, sectors
+    jnl 1f
+    mov di, cx
+    and di, 0x0f        # max 15 sectors
+    shl di, 1
+    shl di, 1           # di = cl*4
+    lea di, [bx+di]
+    mov al, [bp+0]      # track number
+    mov [di+0], al
+    mov al, [bp+2]      # head number
+    mov [di+1], al
+    mov al, cl          # sector number
+    inc al
+    mov [di+2], al
+    movb [di+3], 0x02   # 512 bytes per sector
+    inc cl
+    jmp 0b
+1:
+    mov ah, 0x05        # format track
+    mov al, sectors
+    mov dl, 0           # first drive
+    mov ch, [bp+0]      # track number
+    mov dh, [bp+2]      # head number
+    mov cl, 1           # sector number (first sector?)
+    int 0x13
+    ret
+
+
+readfile:
+    mov ax, [bp+0]
+    mov dx, [bp+2]
+    call fat12_readfile
+    ret
+
+
+    .section .rodata.polmon_str
+polmon_str: .ascii "POLMON  COM"
+polmon_addr = 0x1000
+
+    .section .text.main
+    .global main
+main:
+    cli
+    mov ax, 0x2000      # stack address
+    mov sp, ax          # ss should already be 0
+    sti
+    call dosdbt
+    mov ax, 0x1a00      # first sector of first fat
+    mov dx, 0x1c00      # first sector of root dir
+    call fat12_init
+
+    mov si, 0x80*4
+    movw [si], offset int80h
+    movw [si+2], 0
+
+    mov ax, offset polmon_str 
+    mov dx, polmon_addr
+    call fat12_readfile
+    test ax, ax
+    jnz 0f
+
+    jmp polmon_addr
+0:
+    mov ax, 0x0e42
+    mov bh, 0
+    int 0x10
+    cli
+    hlt
+
+    .section .text.int80h
+int80h:
+    push bx
+    push si
+    push di
+    push bp
+    push ds
+    push es
+    xor cx, cx
+    mov es, cx
+    mov ds, cx
+    shl ah
+    cmp ah, offset int80h_entries
+    jge 0f
+    mov al, ah
+    xor ah, ah
+    mov si, ax
+    mov bp, sp
+    lea bp, [bp + 18]       # 12 for us, 6 for the interrupt
+    call [int80h_table+si]
+    jmp 1f
+0:
+    mov ax, -1
+1:
+    pop es
+    pop ds
+    pop bp
+    pop di
+    pop si
+    pop bx
+    iret
+
+
+    .section .rodata.int80h
+int80h_table:
+    .word offset copy           # 0x00
+    .word offset readsector     # 0x01
+    .word offset writesector    # 0x02
+    .word offset formattrack    # 0x03
+    .word offset readfile       # 0x04
+
+int80h_entries = . - int80h_table

polmon.cc

@@ -1,4 +1,5 @@
 #include <cstdint>
+#include <cstdio>
 
 #ifndef WOZMON
 #define WOZMON 0
@@ -8,7 +9,7 @@
 #define BACKSPACE 0
 #define ASCIIDUMP 0
 #define CLEARSCREENCMD 0
-#define FARCALL 0
+#define INT80H 0
 #define SHOWTITLE 0
 #define BOOTSTRAP 0
 #endif  // WOZMON
@@ -25,8 +26,8 @@
 #define CLEARSCREENCMD 1
 #endif
 
-#ifndef FARCALL
-#define FARCALL 1
+#ifndef INT80H
+#define INT80H 1
 #endif
 
 #ifndef SHOWTITLE
@@ -39,69 +40,54 @@
 
 namespace {
 
-constexpr int kDumpSize = 16;
+#if WOZMON
 
-uint8_t getc() {
-    register uint8_t c asm ("al");
-    asm volatile (
-            "movb $0x00, %%ah\n\t"
-            "int $0x16"
-            : "=r" (c)
-            :: "ah", "cc"
-            );
+int getchar() {
+    register char c asm("al");
+    asm volatile("movb $0x00, %%ah\n\t"
+                 "int $0x16"
+                 : "=r"(c)::"ah", "cc");
     return c;
 }
 
-void putc(uint8_t c) {
-    asm volatile (
-            "push %%bp          \n\t"
-            "movb %0, %%al      \n\t"
-            "movb $0x0e, %%ah   \n\t"
-            "movb $0, %%bh      \n\t"
-            "int $0x10          \n\t"
-            "pop %%bp           \n\t"
-            :: "r" (c)
-            : "ax", "bh", "cc"
-            );
+void putchar(int c) {
+    asm volatile("push %%bp          \n\t"
+                 "mov %0, %%ax       \n\t"
+                 "movb $0x0e, %%ah   \n\t"
+                 "movb $0, %%bh      \n\t"
+                 "int $0x10          \n\t"
+                 "pop %%bp           \n\t" ::"r"(c)
+                 : "ax", "bh", "cc");
 }
 
-void puts(const char* s) {
-    while (*s) {
-        putc(*s++);
-    }
-}
+#endif  // WOZMON
+
+constexpr int kDumpSize = 16;
 
 // arguments on the stack in reverse order
-extern "C" uint16_t Jump(uint16_t addr, int nargs);
-asm (
-        ".section .text.Jump    \n"
-        "Jump:                  \n"
-        "   push %bx            \n"
-        "   push %si            \n"
-        "   push %di            \n"
-        "   push %bp            \n"
-        "   push %es            \n"
-        "   push %ax            \n"  // addr
-        "   movw %sp, %bp       \n"
-        "   movw %dx, %si       \n"  // nargs
-        "   add %si, %si        \n"
-        "j0:                    \n"
-        "   test %si, %si       \n"
-        "   jz j1               \n"
-        "   lea 12(%bp,%si), %di\n"
-        "   push %di            \n"
-        "   sub $2, %si         \n"
-        "   jmp j0              \n"
-        "j1:                    \n"
-        "   lcall *(%bp)        \n"
-        "   add $4, %sp         \n"
-        "   pop %bp             \n"
-        "   pop %di             \n"
-        "   pop %si             \n"
-        "   pop %bx             \n"
-        "   ret"
-        // return value in ax
-        );
+extern "C" uint16_t Int80h(uint8_t fun, int nargs);
+asm(".section .text.Int80h  \n"
+    "Int80h:                \n"
+    "   push %si            \n"
+    "   push %bp            \n"
+    "   mov %al, %ah        \n"
+    "   mov %sp, %bp        \n"
+    "   lea 6(%bp), %si     \n"  // 4 for pushed stuff, 2 for return addr
+    "0:                     \n"
+    "   test %dx, %dx       \n"
+    "   jz 1f               \n"
+    "   push (%si)          \n"
+    "   dec %dx             \n"
+    "   add $2, %si         \n"
+    "   jmp 0b              \n"
+    "1:                     \n"
+    "   int $0x80           \n"
+    "   mov %bp, %sp        \n"
+    "   pop %bp             \n"
+    "   pop %si             \n"
+    "   ret"
+    // return value in ax
+);
 
 constexpr uint8_t kBackspace = 0x7f;
 constexpr uint8_t kOtherBackspace = 0x08;
@@ -126,19 +112,15 @@ uint16_t ReadUintN(int n, const char* buf) {
     return out;
 }
 
-uint8_t ReadUint8(const char* buf) {
-    return ReadUintN(2, buf);
-}
+uint8_t ReadUint8(const char* buf) { return ReadUintN(2, buf); }
 
-uint16_t ReadUint16(const char* buf) {
-    return ReadUintN(4, buf);
-}
+uint16_t ReadUint16(const char* buf) { return ReadUintN(4, buf); }
 
 void WriteHexNibble(uint8_t c) {
     if (c > 9) {
-        putc('a' + c - 10);
+        putchar('a' + c - 10);
     } else {
-        putc('0' + c);
+        putchar('0' + c);
     }
 }
 
@@ -153,53 +135,42 @@ void WriteUint16(uint16_t a) {
 }
 
 uint8_t __get_far_u8__(uint16_t addr, uint16_t seg) {
-    register uint16_t ad asm ("si") = addr;
-    register uint16_t sg asm ("ds") = seg;
-    register uint8_t ret asm ("al");
-    asm (
-            "lodsb              \n\t"
-            : "=r" (ret)
-            : "r" (ad), "r" (sg)
-            );
+    register uint16_t ad asm("si") = addr;
+    register uint16_t sg asm("ds") = seg;
+    register uint8_t ret asm("al");
+    asm("lodsb              \n\t" : "=r"(ret) : "r"(ad), "r"(sg));
     return ret;
 }
 
 void __set_far_u8__(uint16_t addr, uint16_t seg, uint8_t val) {
-    register uint16_t ad asm ("di") = addr;
-    register uint16_t sg asm ("es") = seg;
-    register uint8_t v asm ("al") = val;
-    asm (
-            "stosb      \n\t"
-            :: "r" (sg), "r" (ad), "r" (v)
-            : "memory"
-            );
+    register uint16_t ad asm("di") = addr;
+    register uint16_t sg asm("es") = seg;
+    register uint8_t v asm("al") = val;
+    asm("stosb      \n\t" ::"r"(sg), "r"(ad), "r"(v) : "memory");
 }
 
-__attribute__((noreturn))
-inline static void __basic__() {
-    asm volatile (
-            "movw $0x40, %ax    \n\t"
-            "mov %ax, %ds       \n\t"
-            "int $0x18"
-            );
+__attribute__((noreturn)) inline static void __basic__() {
+    asm volatile("movw $0x40, %ax    \n\t"
+                 "mov %ax, %ds       \n\t"
+                 "int $0x18");
     __builtin_unreachable();
 }
 
 void Dump(uint16_t addr, uint16_t seg, int count) {
     for (int i = 0; i < count; i++) {
-        putc(' ');
+        putchar(' ');
         uint8_t d = __get_far_u8__(addr + i, seg);
         WriteUint8(d);
     }
 #if ASCIIDUMP
-    putc(' ');
-    putc(' ');
+    putchar(' ');
+    putchar(' ');
     for (int i = 0; i < count; i++) {
         uint8_t d = __get_far_u8__(addr + i, seg);
         if (d > 31 && d < 127) {
-            putc(d);
+            putchar(d);
         } else {
-            putc('.');
+            putchar('.');
         }
     }
 #endif
@@ -208,42 +179,38 @@ void Dump(uint16_t addr, uint16_t seg, int count) {
 void DumpHex(uint16_t addr, uint16_t seg) {
     addr &= -kDumpSize;
 
-    putc('[');
+    putchar('[');
     WriteUint16(seg);
-    putc(':');
+    putchar(':');
     WriteUint16(addr);
-    putc(']');
-    putc(':');
+    putchar(']');
+    putchar(':');
     Dump(addr, seg, kDumpSize);
-    putc('\r');
-    putc('\n');
+    putchar('\r');
+    putchar('\n');
 }
 
 void ClearScreen() {
-    asm volatile (
-            "movw $0x0002, %%ax  \n\t"
-            "int $0x10"
-            ::: "ax", "cc"
-            );
+    asm volatile("movw $0x0002, %%ax  \n\t"
+                 "int $0x10" ::
+                         : "ax", "cc");
 }
 
 void Status(uint8_t status) {
-    asm volatile (
-            "xorb %%bh, %%bh    \n\t"
-            "movb $0x03, %%ah   \n\t"
-            "int $0x10          \n\t"
-            "mov %%dx, %%di     \n\t"
-            "movb $0x02, %%ah   \n\t"
-            "movw $77, %%dx     \n\t"
-            "int $0x10          \n\t"
-            "movb %0, %%al      \n\t"
-            "call _ZN12_GLOBAL__N_110WriteUint8Eh   \n\t"
-            "movb $0x02, %%ah   \n\t"
-            "movw %%di, %%dx    \n\t"
-            "int $0x10"
-            :: "rm" (status)
-            : "ax", "bh", "dx", "cx", "di", "cc"
-            );
+    asm volatile("xorb %%bh, %%bh    \n\t"
+                 "movb $0x03, %%ah   \n\t"
+                 "int $0x10          \n\t"
+                 "mov %%dx, %%di     \n\t"
+                 "movb $0x02, %%ah   \n\t"
+                 "movw $77, %%dx     \n\t"
+                 "int $0x10          \n\t"
+                 "movb %0, %%al      \n\t"
+                 "call %1            \n\t"
+                 "movb $0x02, %%ah   \n\t"
+                 "movw %%di, %%dx    \n\t"
+                 "int $0x10" ::"rm"(status),
+                 "l"(WriteUint8)
+                 : "ax", "bh", "dx", "cx", "di", "cc");
 }
 
 bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
@@ -251,38 +218,42 @@ bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
     for (const char* ptr = buf; *ptr;) {
         if (*ptr == 's') {
             cur_addr = 0;
-            cur_seg = ReadUint16(ptr+1);
+            cur_seg = ReadUint16(ptr + 1);
             ptr += 5;
         } else if (*ptr == '$') {
             __basic__();
-        } else if (*ptr == 'r') {
+        } else if (*ptr == 'j') {
+            dump = false;
+            ptr++;
+            auto jump = reinterpret_cast<uint16_t (*)()>(cur_addr);
+            uint16_t ret = jump();
+            WriteUint16(ret);
+            putchar('\r');
+            putchar('\n');
+#if INT80H
+        } else if (*ptr == 'i') {
             dump = false;
-#if FARCALL
             int nargs = 0;
             ptr++;
+            int fun = ReadUint8(ptr);
+            ptr += 2;
             for (; *ptr;) {
                 if (*ptr == ' ') {
                     ptr++;
                     continue;
                 }
                 uint16_t d = ReadUint16(ptr);
-                asm volatile ("push %0" :: "r" (d));
+                asm volatile("push %0" ::"r"(d));
                 nargs++;
                 ptr += 4;
             }
-            uint16_t ret = Jump(cur_addr, nargs);
-            asm volatile (
-                    "shl %0   \n\t"
-                    "add %0, %%sp"
-                    :: "r"(nargs)
-                    );
-            WriteUint16(ret); 
-            putc('\r'); putc('\n');
-#else  // FARCALL
-            auto jump = reinterpret_cast<void(*)()>(cur_addr);
-            jump();
-#endif  // FARCALL
-            ptr++;
+            uint16_t ret = Int80h(fun, nargs);
+            asm volatile("shl %0   \n\t"
+                         "add %0, %%sp" ::"r"(nargs));
+            WriteUint16(ret);
+            putchar('\r');
+            putchar('\n');
+#endif  // INT80H
 #if CLEARSCREENCMD
         } else if (*ptr == 'l') {
             dump = false;
@@ -311,7 +282,10 @@ bool ParseCommand(const char* buf, uint16_t& cur_addr, uint16_t& cur_seg) {
     return dump;
 }
 
-const char* prompt = "> ";
+void DisplayPrompt() {
+    putchar('>');
+    putchar(' ');
+}
 
 void polmon() {
     uint16_t cur_addr = 0;
@@ -321,14 +295,14 @@ void polmon() {
     char* inptr = inbuf;
 
     ClearScreen();
-#if SHOWTITLE    
+#if SHOWTITLE
     puts("PolMon 0.2\r\n");
 #endif  // SHOWTITLE
-    puts(prompt);
+    DisplayPrompt();
 
     while (1) {
-        uint8_t c = getc();
-        putc(c);  // echo
+        uint8_t c = getchar();
+        putchar(c);  // echo
         if (c == '\r') {
             *inptr = 0;
             if (inbuf[0] == 0) {
@@ -336,7 +310,7 @@ void polmon() {
                     cur_addr += kDumpSize;
                 }
             } else {
-                putc('\n');
+                putchar('\n');
             }
 
             if (ParseCommand(inbuf, cur_addr, cur_seg)) {
@@ -344,17 +318,17 @@ void polmon() {
             };
             first = false;
             inptr = inbuf;
-            puts(prompt);
+            DisplayPrompt();
 #if BACKSPACE
         } else if (c == kBackspace || c == kOtherBackspace) {
             inptr--;
             if (inptr < inbuf) {
                 inptr = inbuf;
-                putc(' ');
+                putchar(' ');
                 continue;
             }
-            putc(' ');
-            putc(kOtherBackspace);
+            putchar(' ');
+            putchar(kOtherBackspace);
 #endif
         } else {
             *inptr = c;
@@ -365,13 +339,10 @@ void polmon() {
 
 }  // namespace
 
-int main() {
-    polmon();
-}
+int main() { polmon(); }
 
 #if BOOTSTRAP
-__attribute__((section(".init"), noreturn, used))
-void _start() {
+__attribute__((section(".init"), noreturn, used)) void _start() {
     main();
     __builtin_unreachable();
 }

readio.asm

@@ -0,0 +1,10 @@
+BITS 16
+CPU 8086
+
+_start:
+    mov bp, sp
+    mov si, [bp+4]
+    mov dx, [si]
+    xor ax, ax
+    in al, dx
+    retf 2

stdlib.c

@@ -0,0 +1,25 @@
+int getchar() {
+    register char c asm("al");
+    asm volatile("movb $0x00, %%ah\n\t"
+                 "int $0x16"
+                 : "=r"(c)::"ah", "cc");
+    return c;
+}
+
+int putchar(int c) {
+    asm volatile("push %%bp          \n\t"
+                 "mov %0, %%ax      \n\t"
+                 "movb $0x0e, %%ah   \n\t"
+                 "movb $0, %%bh      \n\t"
+                 "int $0x10          \n\t"
+                 "pop %%bp           \n\t" ::"r"(c)
+                 : "ax", "bh", "cc");
+    return 0;
+}
+
+int puts(const char* s) {
+    while (*s) {
+        putchar(*s++);
+    }
+    return 0;
+}

writeio.asm

@@ -0,0 +1,12 @@
+BITS 16
+CPU 8086
+
+_start:
+    mov bp, sp
+    mov si, [bp+6]
+    mov dx, [si]
+    xor ax, ax
+    mov si, [bp+4]
+    mov al, [si]
+    out dx, al
+    retf 4