;Link port send/receive routines

 include "settings.inc"
 include "ti83plus.inc"
 include "equates.inc" 
 SEGMENT Main
 GLOBALS ON

 EXTERN PutSApp,IGetKey,keyLoop,StartApp,DispHexA

SendByte:
       ld c,a
SendByteC:
       call NZif83Plus
       jr z,has_LA
       ld b,8
loop_byte_send:
       ld de,0FFFFh
       rr c
       jr nc,bit_is_reset
       ld a,2
       jr bit_continue
bit_is_reset:
       ld a,1
bit_continue:
       out (0),a
bit_loop:
       in a,(0)
       and 3
       jr z,bit_done
       in a,(0)
       and 3
       jr z,bit_done
       dec de
       ld a,d
       or e
       jr nz,bit_loop
link_error:
       B_JUMP ErrLinkXmit
bit_done:
       ld a,0
       out (0),a
       ld de,0FFFFh
bit_really_done:
       dec de
       ld a,d
       or e
       jr z,link_error
       in a,(0)
       and 3
       cp 3
       jr nz,bit_really_done
       djnz loop_byte_send
       ret
has_LA:
       call enableLinkAssist_sub
       call reset_delay_counter
       call reset_delay_counter
loc_6B79:
       ld a,0FAh
       ld (9C86h),a
       in a,(9)
       bit 5,a
       jr z,loc_6B88
       ld a,c
       out (0Dh),a
       ret
loc_6B88:
       call NZifTimeout
       jr z,loc_6B79
       B_JUMP ErrLinkXmit

ReceiveByte:
       di
       call ReceiveByteToC
       call RecAByteIO_sub
       ret c
       ret nz
       jr z,ReceiveByte
RecAByteIO_sub:
       cp 1
       ld a,c
       jr nz,$F
       cp 0E0h
       jr z,$F
       B_JUMP ErrLinkXmit
$$:    cp 0E0h
       ret nz
       in a,(2)
       and 80h
       jr z,label1
       in a,(9)
       bit 6,a
       jr nz,label2
       and 19h
       jr nz,label3
label1:
       call sub_6C7F
       jr c,loc_446E
       jr nz,enableLinkAssistCtoA
label2:
       call sub_6CD5
       xor a
       ret
label3:
       ld a,c
       ret
loc_446E:
       nop
enableLinkAssistCtoA:
       call enableLinkAssist
       ld a,c
       or a
       ret
ReceiveByteToC:
       ld b,8
loop_byte:
       call NZif83Plus
       jr z,ReceiveLAByteToC
       ld de,0FFFFh
       jr start_loop
loop:
       in a,(0)
       and 3
       jr nz,$F
errLinkXmit:
       B_JUMP ErrLinkXmit
$$:    cp 3
       jr nz,errLinkXmit
       in a,(0)
       and 3
       jr z,errLinkXmit
       cp 3
       jr nz,ReceiveByteToC_ready
start_loop:
       dec de
       ld a,d
       or e
       jr nz,loop
       jr errLinkXmit
ReceiveByteToC_ready:
       cp 2
       jr z,loc_44D5
       ld a,1
       out (0),a
       rr c
       ld de,0FFFFh
loc_44AE:
       in a,(0)
       and 3
       cp 2
       jr z,loc_44BF
       dec de
       ld a,d
       or e
       jr nz,loc_44AE
       jr errLinkXmit
loc_44BF:
       ld a,0
       out (0),a
       ld d,4
loc_44C5:
       dec d
       jr z,loc_44D0
       in a,(0)
       and 3
       cp 3
       jr nz,loc_44C5
loc_44D0:
       djnz loop_byte
       ld a,0
       ret
loc_44D5:
       ld a,2
       out (0),a
       rr c
       ld de,0FFFFh
loop_2:
       in a,(0)
       and 3
       cp 1
       jr z,loc_44BF
       dec de
       ld a,d
       or e
       jr nz,loop_2
       jr errLinkXmit
NZif83Plus:
       in a,(2)
       and 80h
       xor 80h
       ret
enableLinkAssist:
       call NZif83Plus
       ret nz
enableLinkAssist_sub:
       bit 0,(iy+3Eh)
       ret nz
       set 0,(iy+3Eh)
       in a,(9)
       xor a
       out (8),a
       ret
ReceiveLAByteToC:
       call enableLinkAssist_sub
       call reset_delay_counter
       call reset_delay_counter
receive_loop:
       ld a,0
       ld (9C86h),a
       call NZifTimeout
       jr nz,errLinkXmit
       in a,(9)
       bit 6,a
       jr nz,transmission_error
       and 11h
       jr z,receive_loop
       in a,(0Ah)
       ld c,a
       ld a,0
       ret
transmission_error:
       and 11h
       jr z,errLinkXmit
       in a,(0Ah)
       ld c,a
       ld a,1
       ret
reset_delay_counter:
       push hl
       ld hl,0FFFFh
       in a,(20h)
       and 1
       jr nz,fast_speed
       ld hl,6800h
fast_speed:
       ld (9CACh),hl
       pop hl
       ret
NZifTimeout:
       push hl
       ld h,2
delay_loop:
       dec h
       jr nz,delay_loop
       ld hl,(9CACh)
       dec hl
       ld (9CACh),hl
       ld a,l
       or h
       jr nz,not_timed_out_yet
       ld a,1
       jr timeout
not_timed_out_yet:
       ld a,0
timeout:
       or a
       pop hl
       ret
sub_6C7F:
       push hl
       in a,(2)
       and 80h
       jr z,loc_6CB3
       ld hl,28h
       in a,(20h)
       and 1
       jr nz,loc_6C91
       ld l,10h
loc_6C91:
       dec hl
       ld a,h
       or l
       jr z,loc_6CCF
       in a,(9)
       bit 6,a
       jr nz,loc_6CB0
       bit 4,a
       jr nz,loc_6CCC
       and 8
       jr z,loc_6C91
       in a,(9)
       bit 6,a
       jr nz,loc_6CB0
       and 19h
       jr z,loc_6C91
       jr nz,loc_6CCC
loc_6CB0:
       xor a
       jr loc_6CCC
loc_6CB3:
       ld hl,16h
loc_6CB6:
       dec hl
       ld a,h
       or l
       jr z,loc_6CCF
       in a,(0)
       and 3
       cp 3
       jr z,loc_6CB6
       in a,(0)
       and 3
       cp 3
       jr z,loc_6CB6
       or a
loc_6CCC:
       pop hl
       ld a,c
       ret
loc_6CCF:
       scf
       jr loc_6CCC
sub_6CD5:
       call sub_6CF6
       call sub_6C49
       jr c,errLinkXmit
       in a,(2)
       and 80h
       call nz,sub_6C09
loc_6CE4:
       call ReceiveByteToC
       ld d,a
       ld a,c
       cp 1
       push af
       push de
       call ReceiveByteToC
       pop de
       ld e,a
       pop af
       ld b,a
       ld a,c
       ret
sub_6CF6:
       in a,(2)
       and 80h
       ret z
       in a,(9)
       and 99h
       ret nz
loc_6D00:
       res 0,(iy+3Eh)
       ld a,80h
       out (8),a
       ret
sub_6C49:
       push hl
       in a,(2)
       and 80h
       jr z,loc_6C59
       ld hl,39h
       ld a,(20h)
       and 1
       jr nz,loc_6C5C
loc_6C59:
       ld hl,17h
loc_6C5C:
       dec hl
       ld a,h
       or l
       jr nz,loc_6C6A
       in a,(0)
       and 3
       jr z,loc_6C5C
loc_6C67:
       pop hl
       ld a,c
       ret
loc_6C6A:
       scf
       jr loc_6C67
sub_6C09:
       ld a,80h
       out (8),a
       xor a
       out (8),a
       in a,(9)
       set 0,(iy+3Eh)
       xor a
       ret