Subject: RE: [stella] Maximum baud rate for sending? From: "Fred Quimby" <c9r@xxxxxxxxxxx> Date: Mon, 15 Aug 2005 01:30:22 -0400 |
>This one didn't work for me. I just got a lot of >high-ascii characters. The obvious answer is the out-of-spec signaling, but of course at this speed, cabling becomes really important regardless if the signals are in spec or not. I'm using about 2 feet of thick, stranded copper wires. Not sure if cabling will help. I don't think it's the timing. The timing is pretty good - at 10.329 cycles per bit and 10 bits to send per character, you need 9 of these delays between bits or 92.97 cycles, and I'm using 93. The delays between bits are 10,10,11,10,11,10,11,10,10 cycles, which I think is pretty ideal. Of course, this assumes that the 2600 runs at *exactly* 1.19 Mhz... How accurate is the 2600's clock? I'd like to hear if anyone else gets it to work at 115200. Regardless, if anyone has one of those fancy TTL converters, here's a modified version of the 115200 bps program that should work with one: processor 6502 include "vcs.h" include "macro.h" 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 #$0f cmp #10 bcc noadd adc #6 noadd adc #48 OUT232 LDX #0 ; output low for start bit STX SWCHA LDX #3 ; init count for 4 bit pairs ; EOR #$FF sleep 4 OUT232b STA SWCHA ROR ; rotate out next bit sleep 4 STA SWCHA ROR ; rotate out next bit DEX ; decrement counter BPL 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 Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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