;; This is a dissassembly of the cassette functions in the ;; CPC6128 operating system/firmware ROM. ;; . . . ;;-------------------------------------------------------------- ;; read byte from IX with roms disabled ;; IX = address of byte to read ;; used by cassette functions to read/write a byte ;; C' = current rom selection and mode 057d d9 exx ;; switch to alternative register set 057e 79 ld a,c ;; rom configuration 057f f60c or $0c ;; %00001100 0581 ed79 out (c),a ;; disable upper and lower rom 0583 dd7e00 ld a,(ix+$00) ;; read byte 0586 ed49 out (c),c ;; restore original rom configuration 0588 d9 exx ;; switch back from alternative register set 0589 c9 ret ;;--------------------------------------------------------------- . . . 23fd af xor a 23fe cdde23 call $23de 2401 f3 di 2402 4e ld c,(hl) 2403 3e07 ld a,$07 2405 c36308 jp $0863 2408 cd8124 call $2481 240b 7b ld a,e 240c cdab24 call $24ab 240f d0 ret nc 2410 7e ld a,(hl) 2411 e67f and $7f 2413 c8 ret z 2414 dd7511 ld (ix+$11),l 2417 dd7412 ld (ix+$12),h 241a cd7024 call $2470 241d 1809 jr $2428 ; (+$09) 241f dd6e14 ld l,(ix+$14) 2422 dd6615 ld h,(ix+$15) 2425 dd5e18 ld e,(ix+$18) 2428 4e ld c,(hl) 2429 23 inc hl 242a 7b ld a,e 242b d6f0 sub $f0 242d 3804 jr c,$2433 ; (+$04) 242f 1e00 ld e,$00 2431 180e jr $2441 ; (+$0e) 2433 1d dec e 2434 79 ld a,c 2435 87 add a,a 2436 9f sbc a,a 2437 57 ld d,a 2438 dd7e16 ld a,(ix+$16) 243b 81 add a,c 243c 4f ld c,a 243d dd7e17 ld a,(ix+$17) 2440 8a adc a,d 2441 57 ld d,a 2442 cd8124 call $2481 2445 4e ld c,(hl) 2446 7b ld a,e 2447 b7 or a 2448 2019 jr nz,$2463 ; (+$19) 244a dd7e13 ld a,(ix+$13) 244d 3d dec a 244e 2010 jr nz,$2460 ; (+$10) 2450 dd6e11 ld l,(ix+$11) 2453 dd6612 ld h,(ix+$12) 2456 7e ld a,(hl) 2457 c680 add a,$80 2459 3805 jr c,$2460 ; (+$05) 245b dd360400 ld (ix+$04),$00 245f c9 ret 2460 cd7024 call $2470 2463 dd7318 ld (ix+$18),e 2466 f3 di 2467 dd7105 ld (ix+$05),c 246a dd360480 ld (ix+$04),$80 246e fb ei 246f c9 ret 2470 dd7713 ld (ix+$13),a 2473 23 inc hl 2474 5e ld e,(hl) 2475 23 inc hl 2476 dd7514 ld (ix+$14),l 2479 dd7415 ld (ix+$15),h 247c 7b ld a,e 247d b7 or a 247e c0 ret nz 247f 1c inc e 2480 c9 ret 2481 dd7e00 ld a,(ix+$00) 2484 87 add a,a 2485 f5 push af 2486 dd7116 ld (ix+$16),c 2489 cd6308 call $0863 248c f1 pop af 248d 3c inc a 248e 4a ld c,d 248f dd7117 ld (ix+$17),c 2492 c36308 jp $0863 2495 11a6b2 ld de,$b2a6 2498 1803 jr $249d ; (+$03) 249a 1196b3 ld de,$b396 249d eb ex de,hl 249e cdae24 call $24ae 24a1 eb ex de,hl 24a2 d0 ret nc 24a3 edb0 ldir 24a5 c9 ret 24a6 21a6b2 ld hl,$b2a6 24a9 1803 jr $24ae ; (+$03) 24ab 2196b3 ld hl,$b396 24ae b7 or a 24af c8 ret z 24b0 fe10 cp $10 24b2 d0 ret nc 24b3 011000 ld bc,$0010 24b6 09 add hl,bc 24b7 3d dec a 24b8 20fc jr nz,$24b6 ; (-$04) 24ba 37 scf 24bb c9 ret 24bc cd5725 call $2557 24bf cd9925 call $2599 24c2 af xor a 24c3 cde124 call $24e1 24c6 cdbf2b call $2bbf ; stop cassette motor 24c9 214d01 ld hl,$014d 24cc 3e19 ld a,$19 24ce 29 add hl,hl 24cf 29 add hl,hl 24d0 29 add hl,hl 24d1 29 add hl,hl 24d2 29 add hl,hl 24d3 29 add hl,hl 24d4 0f rrca 24d5 0f rrca 24d6 e63f and $3f 24d8 6f ld l,a 24d9 22e9b1 ld ($b1e9),hl 24dc 3ae7b1 ld a,($b1e7) 24df 37 scf 24e0 c9 ret 24e1 3218b1 ld ($b118),a 24e4 c9 ret 24e5 dd211ab1 ld ix,$b11a 24e9 cd0225 call $2502 24ec e5 push hl 24ed dcac26 call c,$26ac 24f0 e1 pop hl 24f1 d0 ret nc 24f2 ed5b34b1 ld de,($b134) 24f6 ed4b37b1 ld bc,($b137) 24fa 3a31b1 ld a,($b131) 24fd c9 ret 24fe dd215fb1 ld ix,$b15f 2502 dd7e00 ld a,(ix+$00) 2505 b7 or a 2506 3e0e ld a,$0e 2508 c0 ret nz 2509 dde5 push ix 250b e3 ex (sp),hl 250c 34 inc (hl) 250d 23 inc hl 250e 73 ld (hl),e 250f 23 inc hl 2510 72 ld (hl),d 2511 23 inc hl 2512 73 ld (hl),e 2513 23 inc hl 2514 72 ld (hl),d 2515 23 inc hl 2516 eb ex de,hl 2517 e1 pop hl 2518 d5 push de 2519 0e40 ld c,$40 251b af xor a 251c 12 ld (de),a 251d 13 inc de 251e 0d dec c 251f 20fb jr nz,$251c ; (-$05) 2521 d1 pop de 2522 d5 push de 2523 78 ld a,b 2524 fe10 cp $10 2526 3802 jr c,$252a ; (+$02) 2528 0610 ld b,$10 252a 04 inc b 252b 48 ld c,b 252c 1807 jr $2535 ; (+$07) 252e e7 rst $20 252f 23 inc hl 2530 cd2629 call $2926 ; convert character to upper case 2533 12 ld (de),a 2534 13 inc de 2535 10f7 djnz $252e ; (-$09) 2537 0d dec c 2538 2809 jr z,$2543 ; (+$09) 253a 1b dec de 253b 1a ld a,(de) 253c ee20 xor $20 253e 2003 jr nz,$2543 ; (+$03) 2540 12 ld (de),a 2541 18f4 jr $2537 ; (-$0c) 2543 e1 pop hl 2544 dd3415 inc (ix+$15) 2547 dd361716 ld (ix+$17),$16 254b dd351c dec (ix+$1c) 254e 37 scf 254f c9 ret 2550 3a1ab1 ld a,($b11a) 2553 b7 or a 2554 3e0e ld a,$0e 2556 c8 ret z 2557 211ab1 ld hl,$b11a 255a 0601 ld b,$01 255c 7e ld a,(hl) 255d 3600 ld (hl),$00 255f c5 push bc 2560 cd6d25 call $256d 2563 f1 pop af 2564 21e4b1 ld hl,$b1e4 2567 ae xor (hl) 2568 37 scf 2569 c0 ret nz 256a 77 ld (hl),a 256b 9f sbc a,a 256c c9 ret 256d fe04 cp $04 256f d8 ret c 2570 23 inc hl 2571 5e ld e,(hl) 2572 23 inc hl 2573 56 ld d,(hl) 2574 6b ld l,e 2575 62 ld h,d 2576 13 inc de 2577 3600 ld (hl),$00 2579 01ff07 ld bc,$07ff 257c c3a1ba jp $baa1 257f 3a5fb1 ld a,($b15f) 2582 fe03 cp $03 2584 2813 jr z,$2599 ; (+$13) 2586 c6ff add a,$ff 2588 3e0e ld a,$0e 258a d0 ret nc 258b 2175b1 ld hl,$b175 258e 35 dec (hl) 258f 23 inc hl 2590 23 inc hl 2591 7e ld a,(hl) 2592 23 inc hl 2593 b6 or (hl) 2594 37 scf 2595 c48627 call nz,$2786 2598 d0 ret nc 2599 215fb1 ld hl,$b15f 259c 0602 ld b,$02 259e 18bc jr $255c ; (-$44) 25a0 e5 push hl 25a1 d5 push de 25a2 c5 push bc 25a3 0605 ld b,$05 25a5 cdf625 call $25f6 25a8 201a jr nz,$25c4 ; (+$1a) 25aa 2a32b1 ld hl,($b132) 25ad 7c ld a,h 25ae b5 or l 25af 37 scf 25b0 ccac26 call z,$26ac 25b3 300f jr nc,$25c4 ; (+$0f) 25b5 2a32b1 ld hl,($b132) 25b8 2b dec hl 25b9 2232b1 ld ($b132),hl 25bc 2a1db1 ld hl,($b11d) 25bf e7 rst $20 25c0 23 inc hl 25c1 221db1 ld ($b11d),hl 25c4 182c jr $25f2 ; (+$2c) 25c6 e5 push hl 25c7 d5 push de 25c8 c5 push bc 25c9 4f ld c,a 25ca 215fb1 ld hl,$b15f 25cd 0605 ld b,$05 25cf cdf925 call $25f9 25d2 201e jr nz,$25f2 ; (+$1e) 25d4 2a77b1 ld hl,($b177) 25d7 110008 ld de,$0800 25da ed52 sbc hl,de 25dc c5 push bc 25dd d48627 call nc,$2786 25e0 c1 pop bc 25e1 300f jr nc,$25f2 ; (+$0f) 25e3 2a77b1 ld hl,($b177) 25e6 23 inc hl 25e7 2277b1 ld ($b177),hl 25ea 2a62b1 ld hl,($b162) 25ed 71 ld (hl),c 25ee 23 inc hl 25ef 2262b1 ld ($b162),hl 25f2 c1 pop bc 25f3 d1 pop de 25f4 e1 pop hl 25f5 c9 ret 25f6 211ab1 ld hl,$b11a 25f9 7e ld a,(hl) 25fa b8 cp b 25fb c8 ret z 25fc ee01 xor $01 25fe 3e0e ld a,$0e 2600 c0 ret nz 2601 70 ld (hl),b 2602 c9 ret 2603 cda025 call $25a0 2606 d0 ret nc 2607 e5 push hl 2608 2a32b1 ld hl,($b132) 260b 23 inc hl 260c 2232b1 ld ($b132),hl 260f 2a1db1 ld hl,($b11d) 2612 2b dec hl 2613 221db1 ld ($b11d),hl 2616 e1 pop hl 2617 c9 ret 2618 eb ex de,hl 2619 0602 ld b,$02 261b cdf625 call $25f6 261e c0 ret nz 261f ed5334b1 ld ($b134),de 2623 cd3c26 call $263c 2626 2a34b1 ld hl,($b134) 2629 ed5b32b1 ld de,($b132) 262d 19 add hl,de 262e 2234b1 ld ($b134),hl 2631 cdac26 call $26ac 2634 38f0 jr c,$2626 ; (-$10) 2636 c8 ret z 2637 2abeb1 ld hl,($b1be) 263a 37 scf 263b c9 ret 263c 2a1bb1 ld hl,($b11b) 263f ed4b32b1 ld bc,($b132) 2643 7b ld a,e 2644 95 sub l 2645 7a ld a,d 2646 9c sbc a,h 2647 daa1ba jp c,$baa1 264a 09 add hl,bc 264b 2b dec hl 264c eb ex de,hl 264d 09 add hl,bc 264e 2b dec hl 264f eb ex de,hl 2650 c3a7ba jp $baa7 2653 e5 push hl 2654 c5 push bc 2655 4f ld c,a 2656 215fb1 ld hl,$b15f 2659 0602 ld b,$02 265b cdf925 call $25f9 265e 202d jr nz,$268d ; (+$2d) 2660 79 ld a,c 2661 c1 pop bc 2662 e1 pop hl 2663 3276b1 ld ($b176),a 2666 ed537cb1 ld ($b17c),de 266a ed437eb1 ld ($b17e),bc 266e 2260b1 ld ($b160),hl 2671 ed5377b1 ld ($b177),de 2675 21fff7 ld hl,$f7ff 2678 19 add hl,de 2679 3f ccf 267a d8 ret c 267b 210008 ld hl,$0800 267e 2277b1 ld ($b177),hl 2681 eb ex de,hl 2682 ed52 sbc hl,de 2684 e5 push hl 2685 2a60b1 ld hl,($b160) 2688 19 add hl,de 2689 e5 push hl 268a cd8627 call $2786 268d e1 pop hl 268e d1 pop de 268f d0 ret nc 2690 18dc jr $266e ; (-$24) 2692 211ab1 ld hl,$b11a 2695 7e ld a,(hl) 2696 b7 or a 2697 3e0e ld a,$0e 2699 c0 ret nz 269a 3604 ld (hl),$04 269c ed531bb1 ld ($b11b),de 26a0 af xor a 26a1 cde124 call $24e1 26a4 cdb326 call $26b3 26a7 38fb jr c,$26a4 ; (-$05) 26a9 c35725 jp $2557 26ac 3a30b1 ld a,($b130) ; last block flag 26af b7 or a 26b0 3e0f ld a,$0f 26b2 c0 ret nz 26b3 010183 ld bc,$8301 26b6 cde527 call $27e5 26b9 305f jr nc,$271a ; (+$5f) ;; read header ;; ;; B1A4-B1B3 filename ;; B1B4 block number ;; B1B5 last block flag ;; B1B6 file type ;; B1B7,B1B8 length ;; B1B9,B1BA location ;; B1BB first block flag ;; stored header: ;; ;; B11F-B12E filename ;; B12F block number ;; B130 last block flag ;; B131 file type ;; B132,B133 length ;; B134,B135 location ;; B136 first block flag 26bb 21a4b1 ld hl,$b1a4 26be 114000 ld de,$0040 26c1 3e2c ld a,$2c ; header sync 26c3 cda629 call $29a6 ; cas read: read header 26c6 3052 jr nc,$271a ; (+$52) 26c8 068b ld b,$8b ; no message 26ca cd2f29 call $292f ; cassette messages disabled? 26cd 2807 jr z,$26d6 ;; cassette messages are not disabled, so check filenames and display loading ;; message. 26cf cd3727 call $2737 ; compare filenames 26d2 2053 jr nz,$2727 ; if nz, display "Found xxx block x" 26d4 0689 ld b,$89 ; "Loading" 26d6 cd0428 call $2804 ; display "Loading xxx block x" 26d9 ed5bb7b1 ld de,($b1b7) ; length from loaded header 26dd 2a34b1 ld hl,($b134) ; location from stored header 26e0 3a1ab1 ld a,($b11a) 26e3 fe02 cp $02 26e5 280e jr z,$26f5 ; (+$0e) 26e7 21fff7 ld hl,$f7ff 26ea 19 add hl,de 26eb 3e04 ld a,$04 26ed 382b jr c,$271a ; (+$2b) 26ef 2a1bb1 ld hl,($b11b) 26f2 221db1 ld ($b11d),hl 26f5 3e16 ld a,$16 ; data sync 26f7 cda629 call $29a6 ; cas read: read data 26fa 301e jr nc,$271a ; ;; increment block number in internal header 26fc 212fb1 ld hl,$b12f ; block number 26ff 34 inc (hl) ; increment block number ;; get last block flag from loaded header and store into ;; internal header 2700 3ab5b1 ld a,($b1b5) 2703 23 inc hl 2704 77 ld (hl),a ;; clear first block flag 2705 af xor a 2706 3236b1 ld ($b136),a 2709 2ab7b1 ld hl,($b1b7) ; get length from loaded header 270c 2232b1 ld ($b132),hl ; store in internal header 270f cd2f29 call $292f ; cassette messages disabled? 2712 3e8c ld a,$8c ; "OK" 2714 cc7e28 call z,$287e ; display message 2717 37 scf 2718 1865 jr $277f ; (+$65) ;;=========================================================================== 271a b7 or a 271b 211ab1 ld hl,$b11a 271e 2858 jr z,$2778 ; (+$58) 2720 0685 ld b,$85 ; "Read error" 2722 cd8528 call $2885 2725 1894 jr $26bb ; (-$6c) ;;=========================================================================== 2727 f5 push af 2728 0688 ld b,$88 ; "Found " 272a cd0428 call $2804 ; "Found xxx block x" 272d f1 pop af 272e 308b jr nc,$26bb ; (-$75) 2730 0687 ld b,$87 ; "Rewind tape" 2732 cd8328 call $2883 2735 1884 jr $26bb ; (-$7c) ;;======================================================================== ;; compare filenames 2737 3a36b1 ld a,($b136) ; first block flag in internal header? 273a b7 or a 273b 281b jr z,$2758 273d 3abbb1 ld a,($b1bb) ; first block flag in loaded header? 2740 2f cpl 2741 b7 or a 2742 c0 ret nz ;; if user specified a filename, compare it against the filename in the loaded ;; header, otherwise accept the file 2743 3a1fb1 ld a,($b11f) ; did user specify a filename? ; e.g. LOAD"bob 2746 b7 or a 2747 c46027 call nz,$2760 ; compare filenames 274a c0 ret nz ; if filenames do not match, quit ;; gets here if: ;; 1. if a filename was specified by user and filename matches with ;; filename in loaded header ;; ;; 2. no filename was specified by user ;; copy loaded header to internal header 274b 21a4b1 ld hl,$b1a4 274e 111fb1 ld de,$b11f 2751 014000 ld bc,$0040 2754 edb0 ldir 2756 af xor a 2757 c9 ret ;;========================================================================= ;; not first block 2758 cd6027 call $2760 ; compare filenames 275b c0 ret nz 275c eb ex de,hl 275d 1a ld a,(de) 275e be cp (hl) 275f c9 ret ;;============================================================================ ;; compare strings ;; ;; nz = filenames are different ;; z = filenames are identical 2760 211fb1 ld hl,$b11f ; in-memory header 2763 11a4b1 ld de,$b1a4 ; loaded header ;; compare filenames 2766 0610 ld b,$10 ; 16 characters 2768 1a ld a,(de) ; get character from loaded header 2769 cd2629 call $2926 ; convert character to upper case 276c 4f ld c,a 276d 7e ld a,(hl) ; get character from in-memory header 276e cd2629 call $2926 ; convert character to upper case 2771 a9 xor c 2772 c0 ret nz ; quit if characters are not the same 2773 23 inc hl ; increment pointer 2774 13 inc de ; increment pointer 2775 10f1 djnz $2768 ; ;; the filenames are identical 2777 c9 ret ;;============================================================================ 2778 7e ld a,(hl) 2779 3603 ld (hl),$03 277b cd6d25 call $256d 277e b7 or a 277f 9f sbc a,a 2780 f5 push af 2781 cdbf2b call $2bbf ; stop cassette motor 2784 f1 pop af 2785 c9 ret 2786 010284 ld bc,$8402 2789 cde527 call $27e5 278c 304a jr nc,$27d8 ; (+$4a) 278e 068a ld b,$8a 2790 1164b1 ld de,$b164 2793 cd0728 call $2807 2796 217bb1 ld hl,$b17b 2799 cdfa27 call $27fa 279c 303a jr nc,$27d8 ; (+$3a) 279e 2a60b1 ld hl,($b160) 27a1 2262b1 ld ($b162),hl 27a4 2279b1 ld ($b179),hl 27a7 e5 push hl 27a8 2164b1 ld hl,$b164 27ab 114000 ld de,$0040 27ae 3e2c ld a,$2c ; header sync byte 27b0 cdaf29 call $29af ; cas write: write header 27b3 e1 pop hl 27b4 3022 jr nc,$27d8 ; (+$22) 27b6 ed5b77b1 ld de,($b177) 27ba 3e16 ld a,$16 ; data sync byte 27bc cdaf29 call $29af ; cas write: write data block 27bf 2175b1 ld hl,$b175 27c2 dcfa27 call c,$27fa 27c5 3011 jr nc,$27d8 ; (+$11) 27c7 210000 ld hl,$0000 27ca 2277b1 ld ($b177),hl 27cd 2174b1 ld hl,$b174 27d0 34 inc (hl) 27d1 af xor a 27d2 327bb1 ld ($b17b),a 27d5 37 scf 27d6 18a7 jr $277f ; (-$59) 27d8 b7 or a 27d9 215fb1 ld hl,$b15f 27dc 289a jr z,$2778 ; (-$66) 27de 0686 ld b,$86 27e0 cd8528 call $2885 27e3 18b9 jr $279e ; (-$47) 27e5 21e4b1 ld hl,$b1e4 27e8 79 ld a,c 27e9 be cp (hl) 27ea 71 ld (hl),c 27eb 37 scf 27ec e5 push hl 27ed c5 push bc 27ee c4d228 call nz,$28d2 27f1 c1 pop bc 27f2 e1 pop hl 27f3 9f sbc a,a 27f4 d0 ret nc 27f5 cdbb2b call $2bbb ; start cassette motor 27f8 9f sbc a,a 27f9 c9 ret 27fa 7e ld a,(hl) 27fb b7 or a 27fc 37 scf 27fd c8 ret z 27fe 012c01 ld bc,$012c 2801 c3e22b jp $2be2 2804 11a4b1 ld de,$b1a4 2807 3a18b1 ld a,($b118) 280a b7 or a 280b c0 ret nz 280c 3219b1 ld ($b119),a 280f cdf328 call $28f3 2812 cd9828 call $2898 ; display message 2815 1a ld a,(de) ; is first character of filename = 0? 2816 b7 or a 2817 200a jr nz,$2823 ; ;; unnamed file 2819 3e8e ld a,$8e ; "Unnamed file" 281b cd9928 call $2899 ; display message 281e 011000 ld bc,$0010 2821 182e jr $2851 ; (+$2e) ;;----------------------------- ;; named file 2823 cd2f29 call $292f 2826 010010 ld bc,$1000 2829 280d jr z,$2838 ; (+$0d) 282b 6b ld l,e 282c 62 ld h,d 282d 7e ld a,(hl) 282e b7 or a 282f 2804 jr z,$2835 ; (+$04) 2831 0c inc c 2832 23 inc hl 2833 10f8 djnz $282d ; (-$08) 2835 78 ld a,b 2836 41 ld b,c 2837 4f ld c,a 2838 cdfd28 call $28fd ; insert new-line if word ; can't fit onto current-line 283b 1a ld a,(de) ; get character from filename 283c cd2629 call $2926 ; convert character to upper case 283f b7 or a ; zero? 2840 2002 jr nz,$2844 ;; display a space if a zero is found 2842 3e20 ld a,$20 ; display a space 2844 c5 push bc 2845 d5 push de 2846 cd3513 call $1335 ; display character 2849 d1 pop de 284a c1 pop bc 284b 13 inc de 284c 10ed djnz $283b ; (-$13) 284e cdce28 call $28ce ; display space 2851 eb ex de,hl 2852 09 add hl,bc 2853 eb ex de,hl 2854 3e8d ld a,$8d ; "block " 2856 cd9928 call $2899 ; display message 2859 0602 ld b,$02 ; length of word 285b cdfd28 call $28fd ; insert new-line if word ; can't fit onto current-line 285e 1a ld a,(de) 285f cd1429 call $2914 ; display decimal number 2862 cdce28 call $28ce ; display space 2865 13 inc de 2866 cd2f29 call $292f 2869 200b jr nz,$2876 ; (+$0b) 286b 13 inc de 286c 1a ld a,(de) 286d e60f and $0f 286f c624 add a,$24 2871 cdf028 call $28f0 2874 1858 jr $28ce ; display space 2876 1a ld a,(de) 2877 2119b1 ld hl,$b119 287a b6 or (hl) 287b c8 ret z 287c 186d jr $28eb ; (+$6d) 287e cd9928 call $2899 ; display message 2881 1868 jr $28eb ; (+$68) 2883 3eff ld a,$ff ;; display message 2885 f5 push af 2886 cd9128 call $2891 2889 f1 pop af 288a c660 add a,$60 288c d4f028 call nc,$28f0 ; display character 288f 185a jr $28eb ; (+$5a) 2891 cd7c11 call $117c 2894 25 dec h 2895 c4eb28 call nz,$28eb 2898 78 ld a,b ;;========================================================================= ;; display message ;; ;; - message is displayed using word-wrap ;; ;; a = message number (&80-&FF) 2899 e5 push hl 289a e67f and $7f ; get message index (0-127) 289c 47 ld b,a 289d 213529 ld hl,$2935 ; start of message list (points to first message) ;; first message in list? (message 0?) 28a0 2807 jr z,$28a9 ;; not first. ;; ;; - each message is terminated by a zero byte ;; - keep fetching bytes until a zero is found. ;; - if a zero is found, decrement count. If count reaches zero, then ;; the first byte following the zero, is the start of the message we want 28a2 7e ld a,(hl) ; get byte 28a3 23 inc hl ; increment pointer 28a4 b7 or a ; is it zero (0) ? 28a5 20fb jr nz,$28a2 ; if zero, it is the end of this string ;; got a zero byte, so at end of the current string 28a7 10f9 djnz $28a2 ; decrement message count ;; HL = start of message to display ;; this part is looped; message may contain multiple strings ;; end of message? 28a9 7e ld a,(hl) 28aa b7 or a 28ab 2805 jr z,$28b2 ; (+$05) ;; display message 28ad cdb528 call $28b5 ; display message with word-wrap ;; at this point there might be a end of string marker (0), the start ;; of another string (next byte will have bit 7=0) or a continuation string ;; (next byte will have bit 7=1) 28b0 18f7 jr $28a9 ; continue displaying string ;; finished displaying complete string , or displayed part of string sequence 28b2 e1 pop hl 28b3 23 inc hl ; if part of a complete message, go to next sub-string or word 28b4 c9 ret ;;========================================================================= ;; display message with word wrap ;; HL = address of message ;; A = first character in message ;; if -ve, then bit 7 is set. Bit 6..0 define the ID of the message to display ;; if +ve, then this is the first character in the message 28b5 fa9928 jp m,$2899 ;;------------------------------------- ;; count number of letters in word 28b8 e5 push hl ;; store start of word ;; count number of letters in world 28b9 0600 ld b,$00 28bb 04 inc b 28bc 7e ld a,(hl) ;; get character 28bd 23 inc hl ;; increment pointer 28be 07 rlca ;; if bit 7 is set, then this is the last character of the current word 28bf 30fa jr nc,$28bb ;; B = number of letters ;; if word will not fit onto end of current line, insert ;; a line break, and display on next line 28c1 cdfd28 call $28fd 28c4 e1 pop hl ;; restore start of word ;;------------------------------------ ;; display word ;; HL = location of characters ;; B = number of characters 28c5 7e ld a,(hl) ; get byte 28c6 23 inc hl ; increment counter 28c7 e67f and $7f ; isolate byte 28c9 cdf028 call $28f0 ; display char (txt output?) 28cc 10f7 djnz $28c5 ;; display space 28ce 3e20 ld a,$20 ; " " (space) character 28d0 181e jr $28f0 ; display character ;;========================================================================= 28d2 3a18b1 ld a,($b118) 28d5 b7 or a 28d6 37 scf 28d7 c0 ret nz 28d8 cd9128 call $2891 28db cdfe1b call $1bfe 28de cd7612 call $1276 28e1 cddb1c call $1cdb 28e4 cd7e12 call $127e 28e7 fefc cp $fc 28e9 c8 ret z 28ea 37 scf 28eb cdf328 call $28f3 ;; display cr 28ee 3e0a ld a,$0a 28f0 c3fe13 jp $13fe ;;========================================================================== 28f3 f5 push af 28f4 e5 push hl 28f5 3e01 ld a,$01 28f7 cd5a11 call $115a 28fa e1 pop hl 28fb f1 pop af 28fc c9 ret ;;========================================================================== ;; determine if word can be displayed on this line 28fd d5 push de 28fe cd5212 call $1252 2901 5c ld e,h 2902 cd7c11 call $117c 2905 7c ld a,h 2906 3d dec a 2907 83 add a,e 2908 80 add a,b 2909 3d dec a 290a ba cp d 290b d1 pop de 290c d8 ret c 290d 3eff ld a,$ff 290f 3219b1 ld ($b119),a 2912 18d7 jr $28eb ; (-$29) ;;============================================================================ ;; divide by 10 2914 06ff ld b,$ff 2916 04 inc b 2917 d60a sub $0a 2919 30fb jr nc,$2916 ; (-$05) ;; B = result of division by 10 ;; A = <10 291b c63a add a,$3a ; convert to ASCII digit 291d f5 push af 291e 78 ld a,b 291f b7 or a 2920 c41429 call nz,$2914 ; continue with division 2923 f1 pop af 2924 18ca jr $28f0 ; display character ;;============================================================================ ;; convert character to upper case 2926 fe61 cp $61 ; "a" 2928 d8 ret c 2929 fe7b cp $7b ; "z" 292b d0 ret nc 292c c6e0 add a,$e0 292e c9 ret ;;============================================================================ ;; cassette messages ;; if "4" cassette messages are disabled, otherwise they are enabled 292f 3a1ab1 ld a,($b11a) 2932 fe04 cp $04 2934 c9 ret ;;============================================================================ ;; cassette messages ;; - a zero (0) byte indicates end of complete message ;; - a byte with bit 7 set indicates: ;; end of a word, the id of another continuing string ;; 0: "Press" ;; 1: "PLAY then any key:" ;; 2: "error" ;; 3: "Press PLAY then any key:" ;; 4: "Press REC and PLAY then any key:" ;; 5: "Read error" ;; 6: "Write error" ;; 7: "Rewind tape" ;; 8: "Found " ;; 9: "Loading" ;; 10: "Saving" ;; 11: ;; 12: "Ok" ;; 13: "block" ;; 14: "Unnamed file" defb "Pres","s"+&80,0 defb "PLA","Y"+&80,"the","n"+&80,"an","y"+&80,"key",":"+&80,0 defb "erro","r"+&80,0 defb 0+&80,1+&80,0 defb &80,"RE","C"+&80,"an","d"+&80,&81,defb 0 defb "Rea","d"+&80,&82 defb "Writ","e"+&80,&82 defb "Rewin","d"+&80,"tap","e"+&80,0 defb "Found "," "+&80,0 defb "Loadin","g"+&80,0 defb "Savin","g"+&80,0 defb 0 defb "O","k"+&80,0 defb "bloc","k"+&80,0 defb "Unname"d"+&80,"file "," "+&80,0 ;;========================================================================= ;; cas read ;; A = sync byte ;; HL = location of data ;; DE = length of data 29a6 cde329 call $29e3 ; enable key checking and start the cassette motor 29a9 f5 push af 29aa 21282a ld hl,$2a28 ; read block of data 29ad 1819 jr $29c8 ; do read ;;========================================================================= ;; cas write ;; A = sync byte ;; HL = destination location for data ;; DE = length of data 29af cde329 call $29e3 ; enable key checking and start the cassette motor 29b2 f5 push af 29b3 cdd42a call $2ad4 ;; write start of block (pilot and syncs) 29b6 21672a ld hl,$2a67 ;; write block of data 29b9 dc0d2a call c,$2a0d ;; read/write 256 byte blocks 29bc dce92a call c,$2ae9 ;; write trailer 29bf 180f jr $29d0 ;; ;;========================================================================= ;; cas check 29c1 cde329 call $29e3 ; enable key checking and start the cassette motor 29c4 f5 push af 29c5 21372a ld hl,$2a37 ;; check stored block with block in memory ;;------------------------------------------------------ ;; do read ;; cas check or cas read 29c8 e5 push hl 29c9 cd892a call $2a89 ;; read pilot and sync 29cc e1 pop hl 29cd dc0d2a call c,$2a0d ;; read/write 256 byte blocks ;;---------------------------------------------------------------- ;; cas check, cas read or cas write 29d0 d1 pop de 29d1 f5 push af 29d2 0182f7 ld bc,$f782 ;; set PPI port A to output 29d5 ed49 out (c),c 29d7 0110f6 ld bc,$f610 ;; cassette motor on 29da ed49 out (c),c ;; if cassette motor is stopped, then it will stop immediatly ;; if cassette motor is running, then there will not be any pause. 29dc fb ei ;; enable interrupts 29dd 7a ld a,d 29de cdc12b call $2bc1 ;; return previous cassette motor state 29e1 f1 pop af 29e2 c9 ret ;;========================================================================= ;; enable key checking and start the cassette motor ;; store sync byte 29e3 32e5b1 ld ($b1e5),a 29e6 1b dec de 29e7 1c inc e 29e8 e5 push hl 29e9 d5 push de 29ea cde91f call $1fe9 ; ??? 29ed d1 pop de 29ee dde1 pop ix 29f0 cdbb2b call $2bbb ; start cassette motor 29f3 f3 di ;; disable interrupts ;; select PSG register 14 (PSG port A) ;; (keyboard data is connected to PSG port A) 29f4 010ef4 ld bc,$f40e ;; select keyboard line 14 29f7 ed49 out (c),c 29f9 01d0f6 ld bc,$f6d0 ;; cassette motor on + PSG select register operation 29fc ed49 out (c),c 29fe 0e10 ld c,$10 2a00 ed49 out (c),c ;; cassette motor on + PSG inactive operation 2a02 0192f7 ld bc,$f792 ;; set PPI port A to input 2a05 ed49 out (c),c ;; PSG port A data can be read through PPI port A now 2a07 0158f6 ld bc,$f658 ;; cassette motor on + PSG read data operation + select keyboard line 8 2a0a ed49 out (c),c 2a0c c9 ret ;;======================================================================================== ;; read/write blocks ;; DE = number of bytes to read/write ;; D = number of 256 blocks to read/write ;; if D = 0, then there is a single block to write, which has E bytes ;; in it. ;; if D!=0, then there is more than one block to write, write 256 bytes ;; for each block except the last. Then write final block with remaining ;; bytes. 2a0d 7a ld a,d 2a0e b7 or a 2a0f 280d jr z,$2a1e ; (+$0d) ;; do each complete 256 byte block 2a11 e5 push hl 2a12 d5 push de 2a13 1e00 ld e,$00 ; number of bytes 2a15 cd1e2a call $2a1e ; read/write block 2a18 d1 pop de 2a19 e1 pop hl 2a1a d0 ret nc 2a1b 15 dec d 2a1c 20f3 jr nz,$2a11 ; (-$0d) ;; E = number of bytes in last block to write ;;------------------------------------ ;; initialise crc 2a1e 01ffff ld bc,$ffff 2a21 ed43ebb1 ld ($b1eb),bc ;; do function 2a25 1601 ld d,$01 2a27 e9 jp (hl) ;;======================================================================================== ;; IX = address to load data to ;; read data ;; input: ;; D = block size ;; E = actual data size ;; output: ;; D = bytes remaining in block (block size - actual data size) 2a28 cd202b call $2b20 ; read byte from cassette 2a2b d0 ret nc 2a2c dd7700 ld (ix+$00),a ; store byte 2a2f dd23 inc ix ; increment pointer 2a31 15 dec d ; decrement block count 2a32 1d dec e 2a33 20f3 jr nz,$2a28 ; decrement actual data count ;; D = number of bytes remaining in block ;; read remaining bytes in block; but ignore 2a35 1812 jr $2a49 ; (+$12) ;;======================================================================================== ;; check stored block with block in memory 2a37 cd202b call $2b20 ; read byte from cassette 2a3a d0 ret nc 2a3b 47 ld b,a 2a3c cdd7ba call $bad7 ; get byte from IX with roms disabled 2a3f a8 xor b 2a40 3e03 ld a,$03 2a42 c0 ret nz 2a43 dd23 inc ix 2a45 15 dec d 2a46 1d dec e 2a47 20ee jr nz,$2a37 ; (-$12) ;; any more bytes remaining in block?? 2a49 15 dec d 2a4a 2806 jr z,$2a52 ; ;; bytes remaining ;; read the remaining bytes but ignore 2a4c cd202b call $2b20 ; read byte from cassette 2a4f d0 ret nc 2a50 18f7 jr $2a49 ; (-$09) ;;----------------------------------------------------- 2a52 cd162b call $2b16 ; get 1's complemented crc 2a55 cd202b call $2b20 ; read crc byte1 from cassette 2a58 d0 ret nc 2a59 aa xor d 2a5a 2007 jr nz,$2a63 ; (+$07) 2a5c cd202b call $2b20 ; read crc byte2 from cassette 2a5f d0 ret nc 2a60 ab xor e 2a61 37 scf 2a62 c8 ret z 2a63 3e02 ld a,$02 2a65 b7 or a 2a66 c9 ret ;;======================================================================================== ;; write block of data (pad with 0's if less than block size) ;; IX = address of data ;; E = actual byte count ;; D = block size count 2a67 cdd7ba call $bad7 ; get byte from IX with roms disabled 2a6a cd682b call $2b68 ; write data byte 2a6d d0 ret nc 2a6e dd23 inc ix ; increment pointer 2a70 15 dec d ; decrement block size count 2a71 1d dec e ; decrement actual count 2a72 20f3 jr nz,$2a67 ; (-$0d) ;; actual byte count = block size count? 2a74 15 dec d 2a75 2807 jr z,$2a7e ;; no, actual byte count was less than block size ;; pad up to block size with zeros 2a77 af xor a 2a78 cd682b call $2b68 ; write data byte 2a7b d0 ret nc 2a7c 18f6 jr $2a74 ; (-$0a) ;; get 1's complemented crc 2a7e cd162b call $2b16 ;; write crc 1 2a81 cd682b call $2b68 ; write data byte 2a84 d0 ret nc ;; write crc 2 2a85 7b ld a,e 2a86 c3682b jp $2b68 ; write data byte ;;======================================================================================== ;; read pilot and sync 2a89 d5 push de 2a8a cd932a call $2a93 ; read pilot and sync 2a8d d1 pop de 2a8e d8 ret c 2a8f b7 or a 2a90 c8 ret z 2a91 18f6 jr $2a89 ; (-$0a) ;;========================================================================== ;; read pilot and sync ;;--------------------------------- ;; wait for start of leader/pilot 2a93 2e55 ld l,$55 ; %01010101 ; this is used to generate the cassette input data comparison ; used in the edge detection 2a95 cd3d2b call $2b3d ; sample edge 2a98 d0 ret nc ;;------------------------------------------ ;; get 256 pulses of leader/pilot 2a99 110000 ld de,$0000 ; initial total 2a9c 62 ld h,d 2a9d cd3d2b call $2b3d ; sample edge 2aa0 d0 ret nc 2aa1 eb ex de,hl ;; C = measured time ;; add measured time to total 2aa2 0600 ld b,$00 2aa4 09 add hl,bc 2aa5 eb ex de,hl 2aa6 25 dec h 2aa7 20f4 jr nz,$2a9d ; (-$0c) ;; C = duration of last pulse read ;; look for sync bit ;; and adjust the average for every non-sync ;; DE = sum of 256 edges ;; D:E forms a 8.8 fixed point number ;; D = integer part of number (integer average of 256 pulses) ;; E = fractional part of number 2aa9 61 ld h,c ; time of last pulse 2aaa 79 ld a,c 2aab 92 sub d ; subtract initial average 2aac 4f ld c,a 2aad 9f sbc a,a 2aae 47 ld b,a ;; if C>D then BC is +ve; BC = +ve delta ;; if CA ;; average>=previous (possibly read first pulse of sync or second of sync) 2abf 91 sub c ; time of current pulse 2ac0 38e7 jr c,$2aa9 ; carry set if C>(A-H) ;; to get here average>=(previous*2) ;; and this means we have just read the second pulse of the sync bit ;; calculate bit 1 timing 2ac2 7a ld a,d ; average 2ac3 1f rra ; /2 ; A = D/2 2ac4 8a adc a,d ; A = D + (D/2) ; A = D * (3/2) 2ac5 67 ld h,a ; this is the middle time ; to calculate difference between 0 and 1 bit ;; if pulse measured is > this time, then we have a 1 bit ;; if pulse measured is < this time, then we have a 0 bit ;; H = timing constant ;; L = initial cassette data input state 2ac6 22e6b1 ld ($b1e6),hl ;; read sync byte 2ac9 cd202b call $2b20 ; read data-byte 2acc d0 ret nc 2acd 21e5b1 ld hl,$b1e5 ; sync byte 2ad0 ae xor (hl) 2ad1 c0 ret nz 2ad2 37 scf 2ad3 c9 ret ;;======================================================================================== ;; write start of block 2ad4 cdf92b call $2bf9 ;; delay ;; write leader 2ad7 210108 ld hl,$0801 ;; 2049 2ada cdec2a call $2aec ;; write leader (2049 1 bits; 4096 pulses) 2add d0 ret nc ;; write sync bit 2ade b7 or a 2adf cd782b call $2b78 ;; write data-bit 2ae2 d0 ret nc ;; write sync byte 2ae3 3ae5b1 ld a,($b1e5) 2ae6 c3682b jp $2b68 ;; write data byte ;;============================================================================= ;; write trailer = 33 "1" bits 2ae9 212100 ld hl,$0021 ;; 33 ;; check for escape 2aec 06f4 ld b,$f4 ;; PPI port A 2aee ed78 in a,(c) ;; read keyboard data through PPI port A (connected to PSG port A) 2af0 e604 and $04 ;; escape key pressed? ;; bit 2 is 0 if escape key pressed 2af2 c8 ret z ;; write trailer bit 2af3 e5 push hl 2af4 37 scf ;; a "1" bit 2af5 cd782b call $2b78 ;; write data-bit 2af8 e1 pop hl 2af9 2b dec hl ;; decrement trailer bit count 2afa 7c ld a,h 2afb b5 or l 2afc 20ee jr nz,$2aec ; (-$12) 2afe 37 scf 2aff c9 ret ;;============================================================================= ;; update crc 2b00 2aebb1 ld hl,($b1eb) 2b03 ac xor h 2b04 f2102b jp p,$2b10 2b07 7c ld a,h 2b08 ee08 xor $08 2b0a 67 ld h,a 2b0b 7d ld a,l 2b0c ee10 xor $10 2b0e 6f ld l,a 2b0f 37 scf 2b10 ed6a adc hl,hl 2b12 22ebb1 ld ($b1eb),hl 2b15 c9 ret ;;======================================================================================== ;; get stored data crc and 1's complement it 2b16 2aebb1 ld hl,($b1eb) ;; block crc ;; 1's complement crc 2b19 7d ld a,l 2b1a 2f cpl 2b1b 5f ld e,a 2b1c 7c ld a,h 2b1d 2f cpl 2b1e 57 ld d,a 2b1f c9 ret ;;======================================================================================== ;; read data-byte 2b20 d5 push de 2b21 1e08 ld e,$08 2b23 2ae6b1 ld hl,($b1e6) ;; H = timing constant ;; L = initial cassette data input state 2b26 cd442b call $2b44 ;; get edge 2b29 dc4d2b call c,$2b4d ;; get edge 2b2c 300d jr nc,$2b3b 2b2e 7c ld a,h ;; ideal time 2b2f 91 sub c ;; subtract measured time ;; -ve (1 pulse) or +ve (0 pulse) 2b30 9f sbc a,a ;; if -ve, set carry ;; if +ve, clear carry ;; carry flag = bit state: carry set = 1 bit, carry clear = 0 bit 2b31 cb12 rl d ;; shift carry state into bit 0 ;; updating data-byte 2b33 cd002b call $2b00 ;; update crc 2b36 1d dec e 2b37 20ea jr nz,$2b23 ; (-$16) 2b39 7a ld a,d 2b3a 37 scf 2b3b d1 pop de 2b3c c9 ret ;;======================================================================================== ;; sample edge and check for escape ;; L = bit-sequence which is shifted after each edge detected ;; starts of as &55 (%01010101) ;; check for escape 2b3d 06f4 ld b,$f4 ;; PPI port A 2b3f ed78 in a,(c) ;; read keyboard data through PPI port A (connected to PSG port A) 2b41 e604 and $04 ;; escape key pressed? ;; bit 2 is 0 if escape key pressed 2b43 c8 ret z ;; precompensation? 2b44 ed5f ld a,r ;; round up to divisible by 4 ;; i.e. ;; 0->0, ;; 1->4, ;; 2->4, ;; 3->4, ;; 4->8, ;; 5->8 ;; etc 2b46 c603 add a,$03 2b48 0f rrca ;; /2 2b49 0f rrca ;; /4 2b4a e61f and $1f ;; 2b4c 4f ld c,a 2b4d 06f5 ld b,$f5 ; PPI port B input (includes cassette data input) ;; ----------------------------------------------------- ;; loop to count time between edges ;; C = time in 17us units (68T states) ;; carry set = edge arrived within time ;; carry clear = edge arrived too late 2b4f 79 ld a,c ; [1] update edge timer 2b50 c602 add a,$02 ; [2] 2b52 4f ld c,a ; [1] 2b53 380e jr c,$2b63 ; [3] overflow? 2b55 ed78 in a,(c) ; [4] read cassette input data 2b57 ad xor l ; [1] 2b58 e680 and $80 ; [2] isolate cassette input in bit 7 2b5a 20f3 jr nz,$2b4f ; [3] has bit 7 (cassette data input) changed state? ;; pulse successfully read 2b5c af xor a 2b5d ed4f ld r,a 2b5f cb0d rrc l ; toggles between 0 and 1 2b61 37 scf 2b62 c9 ret ;; time-out 2b63 af xor a 2b64 ed4f ld r,a 2b66 3c inc a 2b67 c9 ret ;;======================================================================================== ;; write data byte to cassette ;; A = data byte 2b68 d5 push de 2b69 1e08 ld e,$08 ;; number of bytes 2b6b 57 ld d,a 2b6c cb02 rlc d ;; shift bit into carry 2b6e cd782b call $2b78 ;; write bit to cassette 2b71 3003 jr nc,$2b76 2b73 1d dec e 2b74 20f6 jr nz,$2b6c ;; loop for next bit 2b76 d1 pop de 2b77 c9 ret ;;======================================================================================== ;; write bit to cassette ;; carry flag = state of bit 2b78 ed4be8b1 ld bc,($b1e8) 2b7c 2aeab1 ld hl,($b1ea) 2b7f 9f sbc a,a 2b80 67 ld h,a 2b81 2807 jr z,$2b8a ; (+$07) 2b83 7d ld a,l 2b84 87 add a,a 2b85 80 add a,b 2b86 6f ld l,a 2b87 79 ld a,c 2b88 90 sub b 2b89 4f ld c,a 2b8a 7d ld a,l 2b8b 32e8b1 ld ($b1e8),a ;; write a low level 2b8e 2e0a ld l,$0a ; %00001010 = clear bit 5 (cassette write data) 2b90 cda72b call $2ba7 2b93 3806 jr c,$2b9b ; (+$06) 2b95 91 sub c 2b96 300c jr nc,$2ba4 ; (+$0c) 2b98 2f cpl 2b99 3c inc a 2b9a 4f ld c,a 2b9b 7c ld a,h 2b9c cd002b call $2b00 ; update crc ;; write a high level 2b9f 2e0b ld l,$0b ; %00001011 = set bit 5 (cassette write data) 2ba1 cda72b call $2ba7 2ba4 3e01 ld a,$01 2ba6 c9 ret ;;===================================================================== ;; write level to cassette ;; uses PPI control bit set/clear function ;; L = PPI Control byte ;; bit 7 = 0 ;; bit 3,2,1 = bit index ;; bit 0: 1=bit set, 0=bit clear 2ba7 ed5f ld a,r 2ba9 cb3f srl a 2bab 91 sub c 2bac 3003 jr nc,$2bb1 ; (+$03) ;; delay in 4us (16T-state) units 2bae 3c inc a ; [1] 2baf 20fd jr nz,$2bae ; [3] ;; set low/high level 2bb1 06f7 ld b,$f7 ; PPI control 2bb3 ed69 out (c),l ; set control 2bb5 f5 push af 2bb6 af xor a 2bb7 ed4f ld r,a 2bb9 f1 pop af 2bba c9 ret ;;===================================================================== ;; start cassette motor (if cassette motor was previously off ;; allow to to achieve full rotational speed) 2bbb 3e10 ld a,$10 ; start cassette motor 2bbd 1802 jr $2bc1 ; ;;===================================================================== ;; stop cassette motor 2bbf 3eef ld a,$ef ; stop cassette motor ;;===================================================================== ;; start or stop the cassette motor. ;; ;; - if motor was switched from off->on, delay for a time to allow ;; cassette motor to achieve full rotational speed ;; - if motor was switched from on->off, do nothing ;; bit 4 of register A = cassette motor state 2bc1 c5 push bc 2bc2 06f6 ld b,$f6 ; PPI port C 2bc4 ed48 in c,(c) ; read inputs (includes cassette input data) 2bc6 04 inc b ; PPI control 2bc7 e610 and $10 ; 2bc9 3e08 ld a,$08 ; %00001000 = cassette motor off 2bcb 2801 jr z,$2bce 2bcd 3c inc a ; %00001001 = cassette motor on 2bce ed79 out (c),a ; set motor state 2bd0 37 scf 2bd1 280c jr z,$2bdf 2bd3 79 ld a,c 2bd4 e610 and $10 ; previous state 2bd6 c5 push bc 2bd7 01c800 ld bc,$00c8 2bda 37 scf 2bdb cce22b call z,$2be2 ; delay and check for escape 2bde c1 pop bc 2bdf 79 ld a,c 2be0 c1 pop bc 2be1 c9 ret ;;================================================================= ;; delay & check for escape; allows cassette motor to achieve full ;; rotational speed ;; entry conditions: ;; B = delay factor ;; exit conditions: ;; c = delay completed and escape was not pressed ;; nc = escape was pressed 2be2 c5 push bc 2be3 e5 push hl 2be4 cdf92b call $2bf9 ;; delay 2be7 3e42 ld a,$42 2be9 cd451e call $1e45 ;; check for escape pressed 2bec e1 pop hl 2bed c1 pop bc 2bee 2007 jr nz,$2bf7 ; (+$07) 2bf0 0b dec bc 2bf1 78 ld a,b 2bf2 b1 or c 2bf3 20ed jr nz,$2be2 ; (-$13) 2bf5 37 scf 2bf6 c9 ret ;; escape was pressed 2bf7 af xor a 2bf8 c9 ret ;;======================================================================================== ;; delay 2bf9 018206 ld bc,$0682 ; [3] 2bfc 0b dec bc ; [2] 2bfd 78 ld a,b ; [1] 2bfe b1 or c ; [1] 2bff 20fb jr nz,$2bfc ; [3] 2c01 c9 ret ;;========================================================================================