I got it working at 115200 bps, and it works great! It sends the whole 4k
cart in about 2 seconds. The timing is nearly dead-on.
Plus, the delay loop has been removed, which freed up around 30 bytes, which
could be used to add support for bankswitching, maybe...
processor 6502
include "vcs.h"
include "macro.h"
BIT1 EQU 13 ; 1200 baud
BIT2 EQU 13
ORG $0080
noreset
lda SWCHB
lsr
iny
sty COLUBK
BCS noreset
keepgoing
; ldy #20
; jsr WSYNCY
shit
lda $f000,x
pha
lsr
lsr
lsr
lsr
jsr conv2hex
pla
jsr conv2hex
lda #32
jsr OUT232
inc $f9
lda $f9
and #$0f
sta $f9
bne noret
lda #13
jsr OUT232
noret
inc $fa
ldx $fa
bne keepgoing
inc shit+2
bne keepgoing
brk
conv2hex
and #$0f
cmp #10
bcc noadd
adc #6
noadd
adc #48
OUT232 LDX #$FF ; output low for start bit
STX SWCHA
LDX #4 ; init count for 4 bit pairs
EOR #$FF
sleep 2
OUT232b
STA SWCHA
ROR ; rotate out next bit
sleep 4
STA SWCHA
ROR ; rotate out next bit
DEX ; decrement counter
BNE OUT232b ; loop until 8 bits sent
STX SWCHA
RTS
echo ($f9-*)," bytes free"
.byte
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
.byte
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
start
sei
cld
ldx #$FF
txs
lda #0
clearmem
sta 0,x
dex
bne clearmem
ldx #$7F
loop2
lda $f000,x
sta $80,x
dex
bpl loop2
lda #1
sta SWACNT
lda #$00
sta SWCHA
rerestart
ldy #200
delay
WSYNCY STY WSYNC ; wait a line
DEY ; decrement line counter
BNE WSYNCY ; loop until done
ldx #0
jmp $0080
ORG $107C
.word start+$f80
.word start+$f80
>One more thing, what would the delays have to be to
>send data at the maximum the 2600 can do? So far I've
>only been able to get it up to 2400 baud while doing
>the WSYNC method of delay, otherwise the timing
>doesn't correspond to a standard baud rate and I get
>gibberish in my terminal program.
>
>I'd like to see how fast this can be pushed just as a
>test. If we knew the proper delays then we could use
>the SLEEP macro instead of the WSYNCs. I'm guessing
>that the delay would have to be almost nothing since
>you'd be mostly maxing out the 2600's CPU.
>
>
>
>
>
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