Atari 400 Technical Reference Manual page 316

ERR LINE ADDR B1 B2 B3 B4
SIO ( SERIAL BUS INPUT/OUTPUT CONTROLLER ) PAGE
55
2437 EC8C
AO FF DELAYO: LDY #$FF
2438 EC8E
88 DELAY1 : DEY
2439
EC8F DO FD
BNE DELAY1
2440 EC91 CA
DEX
2441 EC92 DO F8
BNE DELAYO
2442
2443 EC94
20 6B EA JSR SEND
iGO
SEND THE DATA FRAME
2444
2445 EC97 AO 02
LDY #CTIMLO iSET ACK TIME OUT
2446 EC99 A2 00
LDX #CTIMHI
2447 EC9B
20 B9 ED WAITER: JSR SETVBX
2448
2449 EC9E
20 1A EA JSR WAIT
i
WAIT FOR ACK
2450
2451 ECA1 98
TYA
i
IF Y=O, A TIME OUT OR NACK OCCURED
2452
2453 ECA2 60
RTS
i
RETURN
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
i
COMPUTE VALUE FOR POKEY FREG REGS FOR THE BAUD RATE AS
2466
i
MEASURED BY AN INTERVAL OF THE 'VCOUNT' TIMER.
2467
2468 ECA3 8D 10 03 COMPUT: STA
TIMER2
2469 ECA6 8C 11 03
STY TIMER2+1 iSAVE FINAL TIMER VALUE
2470 ECA9 20 04 ED
JSR ADJUST iADJUST VCOUNT VALUE
2471 ECAC 8D 10 03
STA TIMER2 iSAVE ADJUSTED VALUE
2472 ECAF
AD OC 03 LDA TIMER1
2473 ECB2
20 04 ED JSR ADJUST
i
ADJUST
2474
ECB5 8D OC 03
STA TIMER1 iSAVE ADJUSTED TIMER1 VALUE
2475 ECB8 AD 10 03
LDA TIMER2
2476 ECBB 38
SEC
2477 ECBC
ED OC 03 SBC TIMER1
2478
ECBF 8D 12 03
STA
TEMP 1
iFIND VCOUNT DIFFERENCE
2479
ECC2 AD 11 03
LDA
TIMER2+1
2480 ECC5 38
SEC
2481 ECC6
ED 00 03 SBC TIMER1+1
2482 ECC9
A8 TAY
iFIND VBLANK COUNT DIFFERENCE
2483
· IF
PALFLG
2484
LDA #-$9C
2485
HITIMR: CLC
2486
AOC
#$9C
2487
· ENDIF
2488
· IF
PALFLG-1
2489 ECCA
A9 7D
LDA
#-$83
2490 ECCC
18 HITIMR: CLC