memory.mu4

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

loading PIC18 memory

decimal

( Define the basics of the target's memory.)

 2 constant bytes/cell
         -d little-endian

ld target/common/memory.mu4   ( generic memory image support)

| Program memory addresses are 22 bits. The PC is 21 bits, but the largest
| PIC18 parts have only 128 KiB of flash.
|
| I've have only compared two subfamilies - PIC18F1xK50 and the PIC18-Q -
| but it seems that there are *standard* regions defined for the flash, but
| not every chip defines all of them.
|
| The 1xK50, for example, defines Flash, User ID, and Config space, and
| folds the device ID and revision ID into one word at 3f_fffe. The -Q series
| defines *all* of the following:
|
| Flash             : 00_0000 - 1f_ffff
| User IDs          : 20_0000 - 20_001f
| Device info area  : 2c_0000 - 2c_00ff
| Config words      : 30_0000 - 30_????
| EEPROM            : 38_0000 - 38_????
| Device config info: 3c_0000 - 3c_????
| Revision ID       : 3f_fffc - 3f_fffd
| Device ID         : 3f_fffe - 3f_ffff


| Let's define constants for the origins of each of the Flash areas,
| whether they exist or not.

"20_0000 constant @user-id
"2c_0000 constant @device-info    ( unique ID, calibration info)
"30_0000 constant @config
"38_0000 constant @eeprom
"3c_0000 constant @device-config  ( erase page size, number of flash pages, etc)
"3f_fffc constant @revision-id
"3f_fffe constant @device-id

( Two memory aspaces: flash/id/config/eeprom, and data [ram + i/o].)

22 make-aspace  ( flash/id/config/eeprom)
   dup #flash make-image
          dup make-region flash
              make-region boot

      dup 256 make-image  ( XXX how big is big enough?)
              make-region user-id

      dup 256 make-image  ( XXX how big is big enough?)
              make-region config

      #eeprom make-image
              make-region eeprom

| XXX Is the flash space choose-image totally chip-specific? Or can we do
| something like this for everything:

-: ( target)  ( choose an image from an address in flash space)
   dup @user-id u< if  drop flash ^  then
   dup @config  u< if  drop user-id ^  then
       @eeprom  u< if       config ^  then
                            eeprom ;

( Install choose-image in the flash aspace.)
flash 'choose-image !

| Since on some PIC18 families the ram starts at a non-zero offset into
| data space - specifically, at @ram - we want to make sure that the ram
| region - from @ram to @ram #ram + - fits into the ram image, which needs to
| be a power of 2 in size.
|
| The easiest way to do this is to take the larger of @ram and #ram - we
| assume they are both powers of 2! - and double it.

( For the data aspace we keep the default of "drop" for choose-image.)
16 make-aspace  ( data: ram + i/o)
   @ram #ram max 2* make-image  ( ensure that [@ram #ram +] is within the ram image)
                    make-region ram