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loadngo.mac
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loadngo.mac
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; Loader program for the serial bootstrap mode of the Z280 CPU.
; The program is load at address 0, and then waits for an Intel HEX
; file to be loaded.
.z280
CR equ 0Dh
LF equ 0Ah
cseg
LOADER: ld sp,0 ; set stack to top of memory
ld c,8 ; I/O page reg
ld l,0FEh ; UART I/O page
ldctl (c),hl
ld a,11100010b
out (10h),a ; UART config reg
ld a,10000000b
out (12h),a ; UART TX status/ctrl reg
out (14h),a ; UART RX status/ctrl reg
IF 1
ld hl,LOGMSG
call PUTSTR
ENDIF
LOOP: call GETC ; get char
cp ':'
jr z,HEXREC ; branch if start of Intel HEX record
call UCASE
cp 'G'
jr nz,LOOP ; ignore if not a 'G'o command
call PUTC
ld a,' '
call PUTC
call GETHEX ; get start address
ld h,a
call GETHEX
ld l,a
jp (hl) ; exec program
HEXREC: call GETHEX ; get record length
ld b,a ; into reg B
ld c,a ; checksum in reg C
call GETHEX ; get hi addr
ld h,a ; into reg H
add a,c
ld c,a
call GETHEX ; get lo addr
ld l,a ; into reg L
add a,c
ld c,a
call GETHEX ; get record type
or a
jr z,DATA ; branch if data
dec a
ld a,'U'
jr nz,next ; error if not EOF (unknown)
call GETHEX ; get checksum
ld a,'X'
call PUTC ; indicate we're done
ld a,CR
call PUTC
ld a,LF
call PUTC
jp (hl) ; exec program
DATA: add a,c ; update checksum
ld c,a
inc b
dec b
jr z,endrec ; branch if record length is zero
load: call GETHEX ; get data byte
ld (hl),a ; store it
add a,c
ld c,a ; update checksum
inc hl
djnz load
endrec: call GETHEX
add a,c ; checksum must be zero
ld a,'?'
jr nz,next ; else display error
ld a,'.' ; display progress
next: call PUTC
jp LOOP
GETHEX: call GETC
call ASCHEX
rlca
rlca
rlca
rlca
ld e,a
call GETC
call ASCHEX
or e
ret
ASCHEX: call UCASE
sub '0'
cp 10
ret c
sub 7
and 0Fh
ret
UCASE: cp 'a'
ret c
cp 'z'+1
ret nc
and 5Fh
ret
PUTSTR: ld a,(hl)
or a
ret z
call PUTC
inc hl
jr PUTSTR
GETC: in a,(14h) ; UART RX status/ctrl reg
and 10h
jr z,GETC
in a,(16h) ; UART RX data reg
ret
PUTC: ld e,a
twait: in a,(12h) ; UART TX status/ctrl reg
and 01h
jr z,twait
ld a,e
out (18h),a ; UART TX data reg
ret
LOGMSG: db CR,LF,'TinyLoad 1.1'
db CR,LF,'G xxxx when done'
db CR,LF,0
end LOADER