;
; SOME VERY NICE LINK ROUTINES MADE BY PASCAL BOURON
;
; I've made some modifications so it fits ZTetris
;
; Modified further to fit Checkers
;


ReceiveByte:
 ld l, 0	; l used as lcounter
 ld 	 b,8			 ; 8 bits to receive
 ld 	 a,$D0
 out	 (0),a
rb_w_Start:
 in 	 a,(0)
 and $C
 cp  $C				; wait one line becomes low
 jr 	 nz,rb_get_bit
 call Test_ON
 jr 	 rb_w_Start

rb_get_bit:
 ld l, 0    ; reset lcounter
 cp 	 8			; is it a 0 ?
 jr 	 z,rb_receive_zero	; Yeah !
 ld 	 a,$D1
 out	 (0),a			; Ack for a '1'
 rr c				; put the 1 (cf has been set by cp)

rb_waitstop1:
 call Test_On
 in a, (0)
 and $8				; wait 'til Ack is recognized
 jr z, rb_waitstop1
 jr rb_stopok

rb_receive_zero:
 ld 	 a,$d2			; Ack for a '0'
 out	 (0),a
 rr c				; put the 0 (cf has been cleared by cp)

rb_waitStop0:
 call Test_On
 in 	 a,(0)
 and	 $4			; wait 'til Ack is recognized
 jr z, rb_waitStop0

rb_stopok:                      ; here, one line is low cause of us(recv)
 ld 	 a,$d0                  ; the sender calc has already set lines to hi
 out	 (0),a
 djnz 	 rb_w_Start
 ld 	 a,c
 ret


SendByte:
 ld hl,0
 ld (lcounter),hl
 ld 	 b,8
 ld 	 c,a			; byte to send
 ld      d, a			; Save it
 ld 	 a,$D0
 out	 (0),a
w_setport3:
 in 	 a,(0)
 and $C
 cp  $C				; wait both lines are low
 jr 	 z, calc_bit
 call SendTest_ON
 jr 	 w_setport3

calc_bit:
 rr c
 ld a, $d2
 jr 	 c,send_one

send_zero:
 dec a

send_one:
 out	 (0),A

wait_setport:
 call SendTest_ON
 in 	 a,(0)
 and	 $C			; wait both become low
 jr 	 nz,wait_setport
 ld 	 a,$D0			; put them back to hi
 out	 (0),A
 djnz w_setport3
 ld a, d			; Restore byte
 ret


Test_ON:
 ld a,(hrflag)
 or a
 jr z,ShortWait
SendTest_ON:
 bcall(_getcsc)
 cp $0f
 ret nz
 pop hl
 pop hl
 ret

ShortWait:
 dec l
 ret nz  ; exit only if cnt = 0
 pop hl  ;Back to the place you were before.	Gotta love it!
 ld a, $d0
 out (0), a
 xor a
 ret