chat-serial-core.mu4

| This file is part of muforth: https://muforth.dev/
|
| Copyright 2002-2025 David Frech. (Read the LICENSE for details.)

loading PIC18 Serial chat (core)

hex

| Taking inspiration from the wildly successful HC08 serial chat protocol.
|
| Responds to the following commands. NOTE: these are hex values!
|
| 00 - 0f  Idle   - these command bytes are ignored
|
| 10  get-version      - send 4 byte commit (little endian) to host
| 11  set-prog-addr    - set the program (flash) memory address pointer
| 12  set-data-addr    - set the data memory address pointer
| 13  get-data-addr    - get the current value of the data mem ptr
| 14  run              - load PC from flash-addr
| 15  read-prog-n      - read n bytes from program memory, incr pointer
| 16  read-data-n      - read n bytes from data memory, incr pointer
| 17  write-data       - write a byte to data memory, incr pointer
|
| These are Q-series commands for programming the flash, config, and
| eeprom.
|
| 18  set-nvm-addr     - set NVMADR from prog-addr
| 19  nvm-read         - execute an NVM read command, return data read
| 1a  nvm-write        - execute an NVM write command, return status
|
| 1b - ff  Idle   - these command bytes are ignored


| Some useful synonyms. I don't like TBLPTR and TABLAT. They aren't
| mnemonic! TBLPTR points into the program memory space. Why not PROGADR
| and PROGDATA?

aka TBLPTRU  equ PROGADRU
aka TBLPTRH  equ PROGADRH
aka TBLPTRL  equ PROGADRL
aka TABLAT   equ PROGDATA

| We are going to use FSR0 to point to data memory. Let's call it DP - data
| pointer.
|
| XXX Hmm. This collides with my plan to use DP to mean data stack pointer
| everywhere. Maybe DSP/RSP/MSP is better after all?

assembler
aka FSR0       equ DP   ( data pointer)
aka FSR0H      equ DPH  ( data pointer, high byte)

aka POSTINC0   equ @dp+  ( read or write a data memory location, incr pointer)
forth

__meta

boot

0 ,  ( startup rjmp)

( Load device-specific support.)
.ifdef 1xk50
   ld target/PIC18/device/chat-k.mu4
.else
   ld target/PIC18/device/chat-q.mu4
.then

| Compile the first 32 bits of the current muforth Git commit. When asked
| for the version, return these four bytes, in little-endian order.

label get-version
   muforth-commit drop 8 evaluate  >3210
   ldi  send-byte c  ldi  send-byte c  ldi  send-byte c  ldi  send-byte j  ;c

label set-prog-addr
   recv-byte c  PROGADRL ) st
   recv-byte c  PROGADRH ) st
   recv-byte c  PROGADRU ) st  ret  ;c

label set-data-addr
   recv-byte c  DP  ) st
   recv-byte c  DPH ) st  ret  ;c

label get-data-addr
   DP  ) ld  send-byte c
   DPH ) ld  send-byte j  ;c

( Jump indirect to prog-addr.)
label run
   PROGADRU ) ld  PCLATU ) st
   PROGADRH ) ld  PCLATH ) st
   PROGADRL ) ld  PCL    ) st  ( this jumps!) ;c

| Doing streaming reads from program memory space is critical to making
| verifying the flash fast.

( INDF1 points to a scratch byte at the end of ram.)
label read-prog-n
   recv-byte c  INDF1 ) st  ( count)
   begin  prog@+  PROGDATA ) ld  send-byte c  INDF1 ) decsz  again  ret  ;c

| We don't necessarily need to do streaming reads from data space, but it's
| much faster to read multiple bytes at a time. The code is longer, though:
| single byte read is two instructions; multi-byte is seven!

label read-data-n
   recv-byte c  INDF1 ) st  ( count)
   begin  @dp+ ) ld  send-byte c  INDF1 ) decsz  again  ret  ;c

label write-data
   recv-byte c  @dp+ ) st  ret  ;c

label process-serial
   @ram #ram + 1- FSR1 lda  ( point to last byte of ram, as scratch)
   recv-byte c  ( command)   -0f addi
   W ) decsnz  ( 10)  get-version j
   W ) decsnz  ( 11)  set-prog-addr j
   W ) decsnz  ( 12)  set-data-addr j
   W ) decsnz  ( 13)  get-data-addr j
   W ) decsnz  ( 14)  run j
   W ) decsnz  ( 15)  read-prog-n j
   W ) decsnz  ( 16)  read-data-n j
   W ) decsnz  ( 17)  write-data j

.ifndef 1xk50  ( Q-series support)
   W ) decsnz  ( 18)  set-nvm-addr j
   W ) decsnz  ( 19)  nvm-read j
   W ) decsnz  ( 1a)  nvm-write j
.else  ( K50 support)
   ( not yet implemented!)
.then
   ( unknown command)  ret  ;c

here  0 goto  dup \a rjmp  goto
label startup
   chip-init c
   begin  process-serial c  again  ;c