Routines
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EF97: received a whole byte, add it to the buffer
Used by the routine at EF59.
EF97 AC 9B 02 LDY $029B get index to Rx buffer end
EF9A C8 INY increment index
EF9B CC 9C 02 CPY $029C compare with index to Rx buffer start
EF9E F0 2A BEQ $EFCA if buffer full go do Rx overrun error
EFA0 8C 9B 02 STY $029B save index to Rx buffer end
EFA3 88 DEY decrement index
EFA4 A5 AA LDA $AA get assembled byte
EFA6 AE 98 02 LDX $0298 get bit count
EFA9 E0 09 CPX #$09 compare with byte + stop
EFAB F0 04 BEQ $EFB1 branch if all nine bits received
EFAD 4A LSR A else shift byte
EFAE E8 INX increment bit count
EFAF D0 F8 BNE $EFA9 loop, branch always
EFB1 91 F7 STA ($F7),Y save received byte to Rx buffer
EFB3 A9 20 LDA #%00100000 mask 00x0 0000, parity enable bit
EFB5 2C 94 02 BIT $0294 test the pseudo 6551 command register
EFB8 F0 B4 BEQ $EF6E branch if parity disabled
EFBA 30 B1 BMI $EF6D branch if mark or space parity
EFBC A5 A7 LDA $A7 get the RS232 received data bit
EFBE 45 AB EOR $AB EOR with the receiver parity bit
EFC0 F0 03 BEQ $EFC5
EFC2 70 A9 BVS $EF6D if ?? just exit
EFC4 .BYTE $2C makes next line BIT $A650
EFC5 50 A6 BVC $EF6D if ?? just exit
EFC7 A9 01 LDA #$01 set Rx parity error
EFC9 .BYTE $2C makes next line BIT $04A9
EFCA A9 04 LDA #$04 set Rx overrun error
EFCC .BYTE $2C makes next line BIT $80A9
This entry point is used by the routine at EFDB.
EFCD A9 80 LDA #$80 set Rx break error
EFCF .BYTE $2C makes next line BIT $02A9
This entry point is used by the routine at EFDB.
EFD0 A9 02 LDA #$02 set Rx frame error
EFD2 0D 97 02 ORA $0297 OR it with the RS232 status byte
EFD5 8D 97 02 STA $0297 save the RS232 status byte
EFD8 4C 7E EF JMP $EF7E setup to receive an RS232 bit and return
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