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; This loader app is based around the Yahoo app model used in spew.asm, by Cyrano Jones.
; The original comments have been removed/replaced. The code itself of course is also
; replaced to change the functionality, which is to recieve a dynamically specified
; number of bytes. That's all it does. The screen doesn't even update, in order to
; make the binary as small as possible.
; The first two bytes sent from the host make up a 16-bit value of the total number of
; data bytes to follow. The first byte is the low byte, the second is the high. After
; those, the actual data is transferred into ram page 1 in slot8000. The total byte
; count is decremented, and when zero, it jumps to 0x8000 to run the transferred code.
; This was originally written to be assembled using AS80, which can be found at:
; - FyberOptic (
; This has been modified to be assembled with SDCC ASZ80.
.module loader
.area _DATA
.area _HEADER (ABS)
.org 0x4000 ; Apps always start at 0x4000 no matter what
; dataflash page they load from.
jp eventhandler ; Jump to the start of our code.
.dw (icons) ; The following is data about the app
.dw (caption) ; itself, most of which we won't even
.dw (dunno) ; worry about.
.db #0
.dw #0
.dw #0
.dw #0x0001
.dw (endcap - caption - 6) ; num of chars
.dw #0x0006 ; offset to first char
.ascii "Loader" ; the caption string
.dw #0 ; size icon0
.dw (icon0 - icons) ; offset to icon0
.dw #0 ; size icon1
.dw (icon1 - icons) ; offset to icon1 (0x00b5)
.dw #0 ; icon width
.db #0 ; icon height
.dw #0 ; icon width
.db #0 ; icon height
.equ brecvbyte, #0x8027 ; Firmware function in codeflash page 1. Attempts
; to receive a byte. Upon returning, if a = 0, it
; timed out or failed. Otherwise the l register
; holds the received byte.
; Now for the actual code
push bc ; Preserve BC, HL
push hl
xor a ; Put codeflash page 1 into slot8000.
out (#08), a
inc a
out (#07), a
call brecvbyte ; Try to fetch a byte.
or a ; If we didn't get one, try again.
jp z, getbyte2
ld a, l ; Load received byte into A register
pop hl ; Restore BC, HL
pop bc
call getbyte ; Get low byte of total bytes to download
ld l, a
call getbyte ; Get high byte of total bytes to download
ld h, a
ld bc, #0x8000 ; Destination address
call getbyte ; Fetch a byte of data
ld d, a ; Preserve A
ld a, #1 ; Put ram page 1 into slot8000
out (#0x08), a
out (#0x07), a
ld a, d ; Restore A
ld (bc), a ; Load incoming byte to ram.
inc bc ; Inc ram location.
dec hl ; Dec bytes to be received.
xor a ; Check if hl = 0; get another byte if not
or h
jp nz, nextcodebyte
xor a
or l
jp nz, nextcodebyte
jp 0x8000 ; When done, jump to code!