lcd10.s

10 REM > lcd/s v1.10

20 REM Redirect VDU to 40x4 LCD display

30 REM Syntax: lcd (ON|OFF)

40 :

50 REM Sends characters to existing VDU driver, then if in MODE 7 and

60 REM VPOS is in top four lines physical lines, copies display to LCD.

70 :

80 base%=&FC80

90 FOR P=0 TO 1

100 P%=&900

110 [OPT P*3

120 .start

130 JSR old:PHA :\ Send to old WRCH

140 LDA &355:CMP #7:BNE ignore :\ Not mode 7

150 LDA &319:CMP #4:BCS ignore :\ Not top four lines

160 TYA:PHA:TXA:PHA

170 :

180 LDX #0 :\ First controller

190 LDY #0 :\ Start of screen memory

200 .loop

210 LDA #&80+0+0*64 :\ Set address to (0,0)

220 .home

230 BIT base%+0,X:BMI home:STA base%+0,X

240 .char

250 BIT base%+0,X:BMI char :\ Wait until not busy

260 \ Need to translate #_`

270 LDA &7C00,Y:STA base%+1,X :\ Write character

280 INY :\ Step to next character

290 CPY #40:BEQ line1 :\ Move to next line, first controller

300 CPY #120:BEQ line1 :\ Move to next line, second controller

310 CPY #80:BNE next :\ Set to next character

320 LDX #2:BNE loop :\ Step to second controller

330 .line1

340 LDA #&80+0+1*64 :\ Set address to (0,1)

350 .wait

360 BIT base%+0,X:BMI wait:STA base%+0,X

370 .next

380 CPY #160:BNE char :\ Loop back to do next character

390 PLA:TAX:PLA:TAY

400 .ignore

410 PLA:RTS

420 :

430 .old

440 JMP (oldv)

450 :

460 .go%

470 LDA #1:LDX #&A8:LDY #0:JSR &FFDA

480 LDA (&A8),Y:CMP #13:BEQ link_on

490 INY:LDA (&A8),Y:AND #&DF

500 CMP #ASC"F":BNE link_on

510 LDA oldv+0:STA &20E

520 LDA oldv+1:STA &20F

530 RTS

540 .link_on

550 LDA &20E:STA oldv+0

560 LDA &20F:STA oldv+1

570 LDA #start AND 255:STA &20E

580 LDA #start DIV 256:STA &20F

590 RTS

600 .oldv

610 ]NEXT

620 PRINT"*SAVE lcd FFFF0900 ";~P%OR&FFFF0000;" ";~go%OR&FFFF0000