Joshua Wise's Git repositories - fpgaboy.git/blob

1 SECTION "wee",HOME[$0]

2 ; this all needs to be PIC!

3 ; xor a

4 ; ld hl, $FF60

5 ; ld [hli], a

6 ; ld [hli], a

7 ; ld [hli], a

8 st: ld sp, $CFFF

9 nak:

10 ld a, $15 ; NAK

11 call putc+$FF80

13 .ack: call getc+$FF80

14 ; cp $01 ;SOH

15 ; jr z,.soh

16 cp $04 ;EOT

17 jr z, .eot

18 cp $18 ;CAN

19 jr z, .rst

20 jr nak

22 .eot:

23 ld A, $06 ; Ack the EOT

24 call putc+$FF80

25 .rst: rst $00

27 .soh: call getc+$FF80 ; blk

28 call getc+$FF80 ; iblk

29 ld b, $00

30 ld hl, $C000

31 .lp: bit 7, l

32 jr nz, .cksm

33 call getc+$FF80

34 ld [hli], a

35 add b

36 ld b, a

37 jr .lp

38 .cksm: call getc+$FF80

39 cp b

40 jr nz, .donak

41 ld hl, $C000

42 .lp2: ld a, [hli]

43 ld [$FF63], A

44 bit 7, l

45 jr z,.lp2

46 .doack: ld A, $06 ; 06

47 call putc+$FF80

48 jr .ack

49 .donak: call getc+$FF80 ; Wait until the line clears, and then once

50 jr .donak ; that happens, getc will cause a NAK.

52 getc:

53 xor d

54 ;xor e ; Possibly not needed?

55 .dgetc:

56 dec de

57 xor a

58 cp d

59 jr z, .timeout

60 ld a, [$FF53]

61 and $02

62 jr z, .dgetc

63 ld a, [$FF52]

64 ret

65 .timeout:

66 ld hl, $D010

67 ld a, [hl]

68 inc a

69 ld [hl], a

70 ld [$FF51], a

71 pop hl

72 jr nak

74 putc:

75 ld c, $53

76 push af

77 .waitport:

78 ld a,[c]

79 and $01

80 jr nz,.waitport

81 pop af

82 ld [$FF52],a

83 ret

85 section "a", HOME[$7E]

86 nop