Mercurial > hg > Members > kono > nitros9-code
view bootman/llio_6551.a @ 2593:4c3c19ec3257
Added second vhd drive for MESS version 144 and newer. Will not alter
performance with older versions of MESS.
| author | robertgault |
|---|---|
| date | Sat, 24 Dec 2011 13:01:17 +0000 |
| parents | 2db06bc0742a |
| children |
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NAM llio_coco3 TTL CoCo 3 low-level I/O handler PSECT llio_coco3,0,0,0,0,llio VSECT ENDSECT llio: lbsr llinit lbsr llread lbsr llwrite lbsr llterm ********** I/O ROUTINES ********** * 6551 Parameters ADDR EQU $FF68 A_RXD EQU ADDR+$00 A_TXD EQU ADDR+$00 A_STATUS EQU ADDR+$01 A_RESET EQU ADDR+$01 A_CMD EQU ADDR+$02 A_CTRL EQU ADDR+$03 * Baud rates _B2400 EQU $1A 2400 bps, 8-N-1 _B4800 EQU $1C 4800 bps, 8-N-1 _B9600 EQU $1E 9600 bps, 8-N-1 _B19200 EQU $1F 19200 bps, 8-N-1 BAUD EQU _B9600 * ll_init - Initialize the low-level I/O * Exit: Carry = 0: Init success; Carry = 1; Init failed llinit sta A_RESET soft reset (value not important) * Set specific modes and functions: * - no parity, no echo, no Tx interrupt * - no Rx interrupt, enable Tx/Rx lda #$0B sta A_CMD save to command register lda #BAUD sta A_CTRL select proper baud rate * Read any junk rx byte that may be in the register lda A_RXD rts * llread - Read one character from 6551 * * Entry: None * Exit: A = character that was read * * Note, this routine currently doesn't timeout llread r lda A_STATUS get status byte anda #$08 mask rx buffer status flag beq r loop if rx buffer empty lda A_RXD get byte from ACIA data port rts * llwrite - Write one character to 6551 * * Entry: A = character to write * Exit: None llwrite pshs a save byte to write w lda A_STATUS get status byte anda #$10 mask tx buffer status flag beq w loop if tx buffer full puls a get byte sta A_TXD save to ACIA data port rts llterm rts IFNE 0 * llwout - Write an entire string * llwerr - Write an entire string llwerr llwout pshs a l@ lda ,x+ cmpa #C$CR beq e@ leay -1,y beq f@ bsr Write bra l@ e@ bsr Write lda #C$LF bsr Write f@ ldx <buffptr clrb puls a,pc * ReadLine - Read an entire string, up to CR * Entry: X = address to place string being read (CR terminated) * Y = maximum number of bytes to read (including nul byte) ReadLine ldx <buffptr pshs y,x,a ldy #80 l@ bsr Read read 1 character cmpa #C$CR carriage return? beq e@ branch if so... cmpa #$08 backspace? beq bs@ cmpy #$0000 anymore room? beq l@ leay -1,y back up one char sta ,x+ and save in input buffer m@ bsr Write echo back out bra l@ e@ sta ,x bsr Write lda #C$LF bsr Write clrb puls a,x,y,pc bs@ cmpx 1,s are we at start beq l@ if so, do nothing clr ,-x else erase last byte lbsr Write write backspace lda #C$SPAC a space... lbsr Write write it leay 1,y count back up free char lda #$08 another backspace bra m@ ENDC endsect