For those who don't know, WriteToFlash is an undocumented bcall (.equ 50CBh) that has some documentation at http://brandonw.net/calcstuff/WriteToFlash.txt courtesy of BrandonW. It's only available in OS 1.19 and OS 2.40+, and is used by the TI-Navigator app to write appvars directly to the archive. It also used to be the source of an incredibly simple flash unlock exploit 
.
Anyway, I'm working on a library that needs to be able to write appvars directly to flash, so WriteToFlash seemed like a reasonable choice. Unfortunately, the linked documentation seems to be inaccurate.
The code snippet below should, to my understanding, create an appvar TEST with the contents "Hello World" in it in flash, but it doesn't seem to write any data beyond the VAT entry to flash at all. (Which manifests as an ERR:MEMORY in the variable viewer)
I have tested this code, and it fails as expected.
Code:
I'll be trying to look into this more myself; hopefully there's only a slight misunderstanding.
.
Anyway, I'm working on a library that needs to be able to write appvars directly to flash, so WriteToFlash seemed like a reasonable choice. Unfortunately, the linked documentation seems to be inaccurate.
The code snippet below should, to my understanding, create an appvar TEST with the contents "Hello World" in it in flash, but it doesn't seem to write any data beyond the VAT entry to flash at all. (Which manifests as an ERR:MEMORY in the variable viewer)
I have tested this code, and it fails as expected.
Code:
#include "ti83plus.inc"
_WriteToFlash .equ 50CBh
.org $9D93
.db $BB,$6D
;Create a bare VAT entry by creating an appvar and deleting its size bytes
ld hl,name
rst rMOV9TOOP1
ld hl,0
b_call(_CreateAppVar)
push hl ;Save the VAT entry address, needed for WriteToFlash
ex de,hl
ld de,2
b_call(_DelMem)
b_call(_OP4ToOP1) ;CreateAppVar moves OP1 to OP4. Move it back.
pop hl ;VAT entry address
ld a,2 ;Create appvar directly in archive
b_call(_WriteToFlash)
ld hl,text
ld bc,text_end-text ;data length
ld a,3 ;write bytes
b_call(_WriteToFlash)
ld a,4 ;Finish writing
b_call(_WriteToFlash)
ld a,5 ;Mark appvar as valid
b_call(_WriteToFlash)
ret
name:
.db AppVarObj, "TEST", 0
text:
.db "Hello World"
text_end:
.endI'll be trying to look into this more myself; hopefully there's only a slight misunderstanding.
