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t/data/zx81.ctl  view on Meta::CPAN

0313 210940     ld hl, $4009	:C
	:; set start of area to VERSN thereby
	:; preserving RAMTOP etc.
	:;

0316:C
	:#;; OUT-PROG
0316 CD1E03     call $031E	:C OUT_PROG
	:; routine OUT-BYTE
	:;

0319:C
0319 CDFC01     call $01FC	:C
	:; routine LOAD/SAVE                     >>

031C:C
031C 18F8       jr $0316	:C
	:; loop back to OUT-PROG
	:;

031E:C
	:#; -------------------------
	:#; THE 'OUT-BYTE' SUBROUTINE
	:#; -------------------------
	:#; This subroutine outputs a byte a bit at a time to a domestic tape recorder.
	:#
	:#;; OUT-BYTE
031E 5E         ld e, (hl)	:C OUT_BYTE
	:; fetch byte to be saved.

031F:C
031F 37         scf	:C
	:; set carry flag - as a marker.
	:;

0320:C
	:#;; EACH-BIT
0320 CB13       rl e	:C EACH_BIT
	:;  C < 76543210 < C

0322:C
0322 C8         ret z	:C
	:; return when the marker bit has passed 
	:; right through.                        >>
	:;

0323:C
0323 9F         sbc a, a	:C
	:; $FF if set bit or $00 with no carry.

0324:C
0324 E605       and $05	:C
	:; $05               $00

0326:C
0326 C604       add a, $04	:C
	:; $09               $04

0328:C
0328 4F         ld c, a	:C
	:; transfer timer to C. a set bit has a longer
	:; pulse than a reset bit.
	:;

0329:C
	:#;; PULSES
0329 D3FF       out ($FF), a	:C PULSES
	:; pulse to cassette.

032B:C
032B 0623       ld b, $23	:C
	:; set timing constant
	:;

032D:C
	:#;; DELAY-2
032D 10FE       djnz $032D	:C DELAY_2
	:; self-loop to DELAY-2
	:;

032F:C
032F CD460F     call $0F46	:C
	:; routine BREAK-1 test for BREAK key.
	:;

0332:C
	:#;; BREAK-2
0332 3072       jr nc, $03A6	:C BREAK_2
	:; forward with break to REPORT-D
	:;

0334:C
0334 061E       ld b, $1E	:C
	:; set timing value.
	:;

0336:C
	:#;; DELAY-3
0336 10FE       djnz $0336	:C DELAY_3
	:; self-loop to DELAY-3
	:;

0338:C
0338 0D         dec c	:C
	:; decrement counter

0339:C
0339 20EE       jr nz, $0329	:C
	:; loop back to PULSES
	:;

033B:C
	:#;; DELAY-4
033B A7         and a	:C DELAY_4
	:; clear carry for next bit test.

033C:C
033C 10FD       djnz $033B	:C
	:; self loop to DELAY-4 (B is zero - 256)
	:;

t/data/zx81.ctl  view on Meta::CPAN

	:#; the name has been matched in full. 
	:#; proceed to load the data but first increment the high byte of E_LINE, which
	:#; is one of the system variables to be loaded in. Since the low byte is loaded
	:#; before the high byte, it is possible that, at the in-between stage, a false
	:#; value could cause the load to end prematurely - see  LOAD/SAVE check.
	:#
0375 FD3415     inc (iy+$15)	:C
	:; increment system variable E_LINE_hi.

0378:C
0378 210940     ld hl, $4009	:C
	:; start loading at system variable VERSN.
	:;

037B:C
	:#;; IN-PROG
037B 50         ld d, b	:C IN_PROG
	:; set D to zero as indicator.

037C:C
037C CD4C03     call $034C	:C
	:; routine IN-BYTE loads a byte

037F:C
037F 71         ld (hl), c	:C
	:; insert assembled byte in memory.

0380:C
0380 CDFC01     call $01FC	:C
	:; routine LOAD/SAVE                     >>

0383:C
0383 18F6       jr $037B	:C
	:; loop back to IN-PROG
	:;

0385:C
	:#; ---
	:#
	:#; this branch assembles a full byte before exiting normally
	:#; from the IN-BYTE subroutine.
	:#
	:#;; GET-BIT
0385 D5         push de	:C GET_BIT
	:; save the 

0386:C
0386 1E94       ld e, $94	:C
	:; timing value.
	:;

0388:C
	:#;; TRAILER
0388 061A       ld b, $1A	:C TRAILER
	:; counter to twenty six.
	:;

038A:C
	:#;; COUNTER
038A 1D         dec e	:C COUNTER
	:; decrement the measuring timer.

038B:C
038B DBFE       in a, ($FE)	:C
	:; read the

038D:C
038D 17         rla	:C
	:;

038E:C
038E CB7B       bit 7, e	:C
	:;

0390:C
0390 7B         ld a, e	:C
	:;

0391:C
0391 38F5       jr c, $0388	:C
	:; loop back with carry to TRAILER
	:;

0393:C
0393 10F5       djnz $038A	:C
	:; to COUNTER
	:;

0395:C
0395 D1         pop de	:C
	:;

0396:C
0396 2004       jr nz, $039C	:C
	:; to BIT-DONE
	:;

0398:C
0398 FE56       cp $56	:C
	:;

039A:C
039A 30B2       jr nc, $034E	:C
	:; to NEXT-BIT
	:;

039C:C
	:#;; BIT-DONE
039C 3F         ccf	:C BIT_DONE
	:; complement carry flag

039D:C
039D CB11       rl c	:C
	:;

039F:C
039F 30AD       jr nc, $034E	:C
	:; to NEXT-BIT
	:;

03A1:C