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10_devices: - serial.md: expanded with DB-25 pinout, custom chip UART registers, baud rate calculation table, open/configure/read/write patterns, serial debugging (KPrintF/Sushi) - input.md: expanded with handler chain architecture diagram, InputEvent struct, event classes table, qualifier bits, custom handler with key remapping, event consumption/blocking, synthetic event injection, Commodities Exchange Updated indexes: - 07_dos/README.md — enriched descriptions for all files - 10_devices/README.md — enriched descriptions for all files
130 lines
3.6 KiB
Markdown
130 lines
3.6 KiB
Markdown
[← Home](../README.md) · [Devices](README.md)
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# serial.device — UART and RS-232 Communication
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## Overview
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`serial.device` provides access to the Amiga's built-in UART (Universal Asynchronous Receiver/Transmitter) for RS-232 serial communication. The hardware UART is implemented using **CIA-B** shift registers and custom chip DMA. Serial I/O is fundamental for debugging (serial console), modem communication, MIDI, and inter-machine networking.
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---
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## Hardware
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### Serial Port Pins (DB-25)
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| Pin | Signal | Direction | Description |
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|---|---|---|---|
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| 2 | TxD | Output | Transmit data |
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| 3 | RxD | Input | Receive data |
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| 4 | RTS | Output | Request to send (active low) |
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| 5 | CTS | Input | Clear to send (active low) |
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| 6 | DSR | Input | Data set ready |
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| 7 | GND | — | Signal ground |
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| 8 | CD | Input | Carrier detect |
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| 20 | DTR | Output | Data terminal ready |
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### Custom Chip Registers
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| Register | Address | Description |
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|---|---|---|
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| `SERDAT` | `$DFF030` | Serial data write (transmit) — 9 bits: stop bit + 8 data |
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| `SERDATR` | `$DFF018` | Serial data read (receive) — status + received byte |
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| `SERPER` | `$DFF032` | Serial period (baud rate divider) |
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| `ADKCON` | `$DFF09E` | UARTBRK bit for break signal |
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### Baud Rate Calculation
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```c
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/* SERPER value = (system_clock / baud_rate) - 1 */
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/* PAL system clock for serial = 3,546,895 Hz */
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/* NTSC = 3,579,545 Hz */
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#define SERIAL_CLOCK_PAL 3546895
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#define SERIAL_CLOCK_NTSC 3579545
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UWORD serper_from_baud(ULONG baud, BOOL isPAL) {
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return (isPAL ? SERIAL_CLOCK_PAL : SERIAL_CLOCK_NTSC) / baud - 1;
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}
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```
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| Baud Rate | SERPER (PAL) | SERPER (NTSC) |
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|---|---|---|
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| 1200 | 2955 | 2982 |
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| 2400 | 1477 | 1491 |
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| 9600 | 368 | 372 |
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| 19200 | 184 | 185 |
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| 31250 (MIDI) | 112 | 113 |
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| 57600 | 60 | 61 |
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| 115200 | 29 | 30 |
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---
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## Using serial.device
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### Open and Configure
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```c
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struct MsgPort *serialPort = CreateMsgPort();
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struct IOExtSer *serialReq = (struct IOExtSer *)
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CreateIORequest(serialPort, sizeof(struct IOExtSer));
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/* Open serial.device unit 0: */
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BYTE err = OpenDevice("serial.device", 0,
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(struct IORequest *)serialReq, 0);
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/* Configure: */
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serialReq->io_SerFlags = SERF_SHARED | SERF_XDISABLED;
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serialReq->io_Baud = 9600;
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serialReq->io_ReadLen = 8; /* 8 data bits */
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serialReq->io_WriteLen = 8;
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serialReq->io_StopBits = 1;
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serialReq->io_RBufLen = 4096; /* receive buffer size */
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serialReq->IOSer.io_Command = SDCMD_SETPARAMS;
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DoIO((struct IORequest *)serialReq);
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```
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### Write Data
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```c
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serialReq->IOSer.io_Command = CMD_WRITE;
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serialReq->IOSer.io_Data = "Hello Serial\r\n";
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serialReq->IOSer.io_Length = 14;
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DoIO((struct IORequest *)serialReq);
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```
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### Read Data
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```c
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/* Check how many bytes are waiting: */
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serialReq->IOSer.io_Command = SDCMD_QUERY;
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DoIO((struct IORequest *)serialReq);
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ULONG waiting = serialReq->IOSer.io_Actual;
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if (waiting > 0) {
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serialReq->IOSer.io_Command = CMD_READ;
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serialReq->IOSer.io_Data = buffer;
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serialReq->IOSer.io_Length = waiting;
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DoIO((struct IORequest *)serialReq);
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/* buffer now contains received data */
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}
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```
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### Serial Debugging
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Many developers use a null-modem cable to a terminal for kernel debugging:
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```c
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/* Kprintf — ROM debug output via serial (ROMTags/exec): */
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/* This bypasses serial.device entirely — writes directly to SERDAT */
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void KPrintF(const char *fmt, ...); /* available in debug ROMs */
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/* Sushi/Sashimi — capture serial debug output on another Amiga */
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```
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---
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## References
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- NDK39: `devices/serial.h`
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- HRM: *Amiga Hardware Reference Manual* — Serial Port chapter
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- ADCD 2.1: serial.device autodocs
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