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Graphics: text_fonts (bitmap layout, styles), sprites (DMA, multiplexing), gfx_base (chipset detection), rastport (draw modes, clipping), ham_ehb (mermaid fixes), display_modes (HAM palettes) Devices: scsi (per-model interfaces, Gayle limits, CD-ROM, native vs vendor drivers), console (ANSI sequences, CON:/RAW:), parallel (CIA registers, pinout), timer (resource exhaustion), gameport (quadrature, XOR state) Libraries: workbench (WBStartup, AppWindow/Icon/MenuItem), rexxsyslib (ARexx port hosting, command parsing), diskfont (font directory, colour fonts), keymap (rawkey codes, dead keys), locale (catalogue system, date formatting), layers (ClipRect, refresh types), utility (TagItem chains), icon (DiskObject, ToolTypes), iffparse (IFF structure, ByteRun1), expansion (Zorro AutoConfig) Networking: tcp_ip_stacks (major rewrite - Amiga vs Unix architecture, SANA-II pipeline, PPP/SLIP dial-up, Ethernet cards, MiSTer), bsdsocket (pure API ref), sana2 (buffer hooks, driver requirements), protocols (all code examples). Deduplicated overlap between the three files. Toolchain: debugging (Enforcer patterns, SnoopDOS, GDB remote, kprintf checklist), sasc (pragma encoding, __saveds idioms), stormc (NEW - StormC IDE, C++, PowerPC) References: error_codes (DOS, Exec, trackdisk, Intuition error tables) Driver development: rtg_driver (Native driver analysis, P96 tuning) All 22 README indexes updated. Root README synced with stormc.md entry.
149 lines
4.3 KiB
Markdown
149 lines
4.3 KiB
Markdown
[← Home](../README.md) · [Devices](README.md)
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# parallel.device — Centronics Parallel Port
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## Overview
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`parallel.device` provides I/O for the Amiga's Centronics-compatible 25-pin parallel port. Primarily used for printers, it also serves as a general-purpose 8-bit data port for hardware projects, dongles, MIDI interfaces, and inter-machine transfers (Laplink-style).
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The parallel port is directly connected to **CIA-A** Port B data register (`$BFE101`) with handshake lines on CIA-A and CIA-B.
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```mermaid
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flowchart LR
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APP["Application"] -->|"CMD_WRITE<br/>CMD_READ"| PAR["parallel.device"]
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PAR --> CIA["CIA-A Port B<br/>($BFE101)<br/>8 data bits"]
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CIA --> PORT["DB-25 Connector<br/>(pins 2-9 = data)"]
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PAR --> CIAB["CIA-B<br/>Handshake lines"]
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style PAR fill:#e8f4fd,stroke:#2196f3,color:#333
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style CIA fill:#c8e6c9,stroke:#2e7d32,color:#333
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```
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---
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## Hardware Pinout
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| Pin | Signal | Direction | Description |
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|---|---|---|---|
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| 1 | /STROBE | Output | Data strobe (active low) |
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| 2–9 | D0–D7 | I/O | 8-bit bidirectional data |
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| 10 | /ACK | Input | Acknowledge from printer |
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| 11 | BUSY | Input | Printer busy |
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| 12 | POUT | Input | Paper out |
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| 13 | SELECT | Input | Printer selected |
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| 14–17 | — | — | Reserved / unused |
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| 18–25 | GND | — | Ground |
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---
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## Opening
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```c
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struct MsgPort *parPort = CreateMsgPort();
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struct IOExtPar *par = (struct IOExtPar *)
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CreateIORequest(parPort, sizeof(struct IOExtPar));
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if (OpenDevice("parallel.device", 0, (struct IORequest *)par, 0))
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{
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Printf("Cannot open parallel.device\n");
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/* Port may be in use by another application (printer, etc.) */
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}
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```
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> [!NOTE]
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> Only **one** application can have the parallel port open at a time. If the port is busy (e.g., printer spooler has it), `OpenDevice` will fail. This is unlike serial.device which supports shared modes.
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---
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## Commands
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| Code | Constant | Description |
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|---|---|---|
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| 2 | `CMD_READ` | Read bytes (bidirectional mode) |
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| 3 | `CMD_WRITE` | Write bytes to the port |
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| 5 | `CMD_CLEAR` | Clear internal buffers |
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| 7 | `CMD_RESET` | Reset the device |
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| 8 | `CMD_FLUSH` | Abort all pending I/O |
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| 9 | `PDCMD_QUERY` | Get port status (busy, paper out, etc.) |
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| 10 | `PDCMD_SETPARAMS` | Configure port parameters |
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### Writing Data
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```c
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/* Send data to the parallel port: */
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char printData[] = "Hello, Printer!\r\n";
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par->IOPar.io_Command = CMD_WRITE;
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par->IOPar.io_Data = printData;
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par->IOPar.io_Length = sizeof(printData) - 1;
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DoIO((struct IORequest *)par);
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if (par->IOPar.io_Error)
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Printf("Write error: %ld\n", par->IOPar.io_Error);
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```
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### Querying Status
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```c
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par->IOPar.io_Command = PDCMD_QUERY;
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DoIO((struct IORequest *)par);
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UBYTE status = par->io_Status;
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if (status & IOPTF_PARBUSY) Printf("Printer busy\n");
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if (status & IOPTF_PAPEROUT) Printf("Paper out\n");
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if (status & IOPTF_PARSEL) Printf("Printer selected\n");
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```
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### Setting Parameters
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```c
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/* Configure for custom use (e.g., no handshaking): */
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par->IOPar.io_Command = PDCMD_SETPARAMS;
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par->io_ParFlags = PARF_SHARED; /* shared access (OS 2.0+) */
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DoIO((struct IORequest *)par);
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```
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---
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## Direct Hardware Access
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For hardware projects that need precise control (bypassing the device driver):
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```c
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/* Direct CIA-A Port B access: */
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volatile UBYTE *ciaaPrb = (UBYTE *)0xBFE101; /* data register */
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volatile UBYTE *ciaaDdrb = (UBYTE *)0xBFE301; /* data direction */
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/* Set all 8 bits as output: */
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*ciaaDdrb = 0xFF;
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/* Write a byte: */
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*ciaaPrb = 0x42;
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/* Set as input: */
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*ciaaDdrb = 0x00;
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UBYTE value = *ciaaPrb;
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```
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> [!CAUTION]
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> Direct hardware access bypasses the OS completely. Do not mix direct register access with parallel.device operations — close the device first or don't open it at all.
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---
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## Common Uses
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| Use Case | Method |
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| Printer output | `CMD_WRITE` through printer.device (which opens parallel.device) |
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| Hardware dongle | Direct CIA-A Port B register read |
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| MIDI interface | Parallel-to-MIDI adapter with custom timing |
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| Amiga-to-PC transfer | Laplink cable with ParNet or ParBench software |
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| Sampling hardware | ADC/DAC connected to data lines |
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---
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## References
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- NDK39: `devices/parallel.h`
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- ADCD 2.1: parallel.device autodocs
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- See also: [serial.md](serial.md) — serial port I/O
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- See also: [cia_chips.md](../01_hardware/common/cia_chips.md) — CIA register details
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