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.PAG 'IEEE'
;ATN IRQ PROCESS
; IRQ ON ATN, LISTEN TO PET
; CLEAR STACK
.SKI 3
ATNIRQ LDX #$FF
STX CMDNUM
TXS
LDA ATNPE ;CLEAR IRQ FLAG
LDA #DAVO+EOIO
ORA PAD2 ;FREE CONTROL LINES
STA PAD2
LDA #255
STA IEEEDO ;FREE DATA LINES
ATN10 LDA #DACO+RFDO+ATNA
ORA PAD2
STA PAD2
ATN20 BIT PAD2
BVC ATN30 ;DAV LO
BMI ATN20 ;ATN LO ATNI HI
BPL ATN50 ;ATN HI
ATN30 LDA #255-RFDO ;NRFD LO
AND PAD2
STA PAD2
AND #EOII
STA EOIFLG ;SAVE EOI
LDA IEEEDI
EOR #$FF
STA DATA ;SAVE COMMAND
LDA #255-DACO ;NDAC HI
AND PAD2
STA PAD2
DCDE LDY #0
LDA DATA
AND #%01100000
CMP #$40 ;TALK?
BEQ DCDE60
CMP #$20 ;LISTEN?
BEQ DCDE20
CMP #$60 ;SECONDARY?
BEQ DCDE70
BNE DCDE80 ;OTHER
DCDE20 LDA DATA
CMP LSNADR
BEQ DCDE40 ;MY LISTEN ADDRESS
CMP #UNLSN
BNE DCDE30
STY LSNACT
DCDE30 STY ADRSED ;NOT PRIMARY ADDRSED
JMP DCDE80
DCDE40 STA LSNACT
STY TLKACT
DCDE50 LDA #32
STA SA ;DEFAULT SA
STA ORGSA
STA ADRSED ;PRIMARY ADDRESSED
BNE DCDE80
DCDE60 STY TLKACT
LDA DATA
CMP TLKADR
BNE DCDE30
STA TLKACT
STY LSNACT
BEQ DCDE50
DCDE70 LDA ADRSED
BEQ DCDE80 ;NOT ADDRESSED
LDA DATA
STA ORGSA
PHA
AND #$F
STA SA
PLA
AND #$F0 ;CLOSE?
CMP #$E0
BNE DCDE80
JSR CLOSE
DCDE80
ATN40 BIT PAD2
BVC ATN40
JMP ATN10
ATN50 LDA LSNACT
BEQ ATN60
LDA #255-RFDO-ATNA
AND PAD2
STA PAD2
CLI
JSR LISTEN
JMP IDLE
ATN60 LDA #255-ATNA-DACO
AND PAD2
STA PAD2
LDA TLKACT
BEQ ATN70
CLI
JSR TALK
ATN70 JMP IDLE
.SKI 5
LISTEN LDA #RFDO ;RFD: HI
ORA PAD2
STA PAD2
LSN10 BIT PAD2 ;DAV: LO
BVS LSN10
JSR FNDWCH ; WAS LDX SA
BCS LSN15
.SKIP
LDA CHNRDY,X
ROR A ;OK, OPEN FOR LISTEN
BCS LSN30
LSN15 LDA ORGSA ; WAS TXA
AND #$F0 ;SA=OPEN?
CMP #$F0
BEQ LSN30
LSN20 LDA SA
CMP #1
BEQ LSN25
LSN21 BIT PAD2
BVC LSN21
LDA #255-DACO
AND PAD2
STA PAD2
RTS
.SKIP
LSN25 LDA #255-RFDO ; ACCEPT ALL DATA
AND PAD2
STA PAD2 ;RFD LOW
LDA #255-DACO
AND PAD2 ; DAC HI
STA PAD2
.SKIP
LSN26 BIT PAD2 ; DAV HI
BVC LSN26
LDA #DACO
ORA PAD2 ; DAC LOW
STA PAD2
LDA #RFDO ; RFD HI
ORA PAD2
STA PAD2
LSN28 BIT PAD2 ; WAIT DAV LOW
BVC LSN28
JMP LSN25 ; DO UNTIL ATN PULLED
LSN30 LDA #255-RFDO
AND PAD2
STA PAD2
AND #EOII
STA EOIFLG
LDA IEEEDI
EOR #$FF
STA DATA
SEI
LDA #255-DACO
AND PAD2
STA PAD2
LSN40 BIT PAD2
BVC LSN40
LDA #DACO
ORA PAD2
STA PAD2
JSR PUT
LSTRTN CLI
JMP LISTEN
.SKI 3
TALK JSR FNDRCH
BCS NOTLK ; TEST IF CHANNEL READY
TALK1 LDX LINDX
LDA CHNRDY,X
BMI TLK10
NOTLK RTS
TLK10 BIT PBD2 ;RFD: HI
BPL TLK10
LDA CHNDAT,X
EOR #$FF
STA IEEEDO
LDA CHNRDY,X
ORA #255-EOIO-DAVO ;DAV: LO
AND PAD2
STA PAD2
TLK20 BIT PBD2
BPL TLK30
BVC TLK20
LDA #DAVO+EOIO
ORA PAD2
STA PAD2
JMP IDLE
TLK30 JSR GET
TLK35 BIT PBD2
BVC TLK35
TLKRTN LDA #$FF
STA IEEEDO
LDA #DAVO+EOIO
ORA PAD2
STA PAD2
TLK40 BIT PBD2
BVS TLK40
BVC TALK1
.END