Atari 400 Technical Reference Manual page 382

ERR LINE
ADDR
B1 B2 B3 B4
DISPLAY HANDLER -- 10-30-78 -- DISPLC
PAGE 121
5437 FD5A E6 78 INC
DELTAC+1
5438 FD5C A2 02 DRAW2: LOX
#2
iZERO RAM FOR DRAW LOOP
5439 FDSE AO 00 LDY #0
5440
FD60 84 73 STY COLAC+1
5441 FD62
98
DRAW3A: TYA
5442 FD63 95 70 STA
ROWAC, X
5443 FD65 B5 SA LDA
OLDROW, X
5444 FD67 95 54 STA ROWCRS,X
5445 FD69
CA DEX
5446 FD6A 10 F6 BPL DRAW3A
5447 FD6C A5 77 LDA
DELTAC iFIND LARGER ONE (ROW OR COL)
5448 .
STA
COUNTR (PREPARE COUNTR AND ENDPT)
5449 STA
ENDPT
5450 FD6E E8 INX
i
MAKE X 0
5451 FD6F A8 TAY
5452 FD70 A5 78 LDA
DELTAC+1
5453 FD72 85 7F STA COUNTR+1
5454
FD74
85 75
STA ENDPT+l
5455 FD76 DO OB BNE DRAW3
,AUTOMATICALLY LARGER IF MSD>O
5456 FD78 A5 77
LDA DELTAC
5457 FD7A C5 76 CMP DELTAR
iLOW COL )LOW ROW?
5458 FD7C BO 05 BCS
DRAW3 ; YES
5459 FD7E A5 76 LDA DEL TAR
5460 FD80 A2 02 LDX #2
5461 FD82 A8 TAY
5462 FD83
98
DRAW3: TYA
iPUT IN INITIAL CONDITIONS
5463 FD84
85 7E
STA COUNTR
5464 FD86 85 74 STA ENDPT
5465 FD88
48
PHA
i
SAVE AC
5466 FD89 A5 75 LDA ENDPT+l ;PUT LSB OF HIGH BYTE
5467 FD8B 4A LSR A ; INTO CARRY
5468 FD8C 68 PLA ; RESTORE AC
5469
FD9D
6A
RDR A
iROR
TH~
9 BIT ACUMULATOR
5470 FD8E 95 70 STA ROWAC, X
5471 FD90 AS 7E DRAW4A: LDA COUNTR
i
TEST ZERO
5472 FD92 05 7F ORA COUNTR+l
5473 FD94
DO 03
BNE DRAW11
i
IF COUNTER IS ZERO, LEAVE DRAW
5474 FD96 4C 42 FE JMP
DRAW10
5475 FD99 18 DRAWll : CLC
iADD ROW TO ROWAC (PLOT LOOP)
5476 FD9A A5 70 LOA ROWAC
5477 FD9C 65 76 ADC DEL TAR
5478 FD9E 85 70 STA ROWAC
5479 FDAO 90 02 BCC DRAW5
5480 FDA2 E6 71 INC ROWAC+1
5481 FDA4 AS 71 DRAW5: LDA ROWAC+1 ; COMPARE ROW TO ENDPOINT
5482 FDA6 C5 7S CMP ENDPT+l
,IF HIGH BYTE OF ROW IS .LT. HIGH
5483 FDA8
90 14
BCC DRAW6 i BYTE OF ENDPT, BLT TO COLUMN
5484
FDAA
DO 06
BNE DRAW5A
5485 FDAC
AS 70
LDA ROWAC
5486
FDAE
C5 74
CMP ENDPT i LOW BYTE
5487 FDBO 90 OC
BCC DRAW6 i ALSO BLT
5488 FDB2 18
DRAW5A: CLC iGE SO MOVE POINT
5489 FDB3 A5 54 LDA ROWCRS
5490 FDB5 65 79 ADC
ROW INC