| C64 ROM | Routines |
| Prev: EDFE | Up: Map | Next: EE85 |
| EE13 | 78 | SEI | disable the interrupts | |
| EE14 | A9 00 | LDA #$00 | set 0 bits to do, will flag EOI on timeour | |
| EE16 | 85 A5 | STA $A5 | save the serial bus bit count | |
| EE18 | 20 85 EE | JSR $EE85 | set the serial clock out high | |
| EE1B | 20 A9 EE | JSR $EEA9 | get the serial data status in Cb | |
| EE1E | 10 FB | BPL $EE1B | loop if the serial clock is low | |
| EE20 | A9 01 | LDA #$01 | set the timeout count high byte | |
| EE22 | 8D 07 DC | STA $DC07 | save VIA 1 timer B high byte | |
| EE25 | A9 19 | LDA #$19 | load timer B, timer B single shot, start timer B | |
| EE27 | 8D 0F DC | STA $DC0F | save VIA 1 CRB | |
| EE2A | 20 97 EE | JSR $EE97 | set the serial data out high | |
| EE2D | AD 0D DC | LDA $DC0D | read VIA 1 ICR | |
| EE30 | AD 0D DC | LDA $DC0D | read VIA 1 ICR | |
| EE33 | 29 02 | AND #%00000010 | mask 0000 00x0, timer A interrupt | |
| EE35 | D0 07 | BNE $EE3E | if timer A interrupt go ?? | |
| EE37 | 20 A9 EE | JSR $EEA9 | get the serial data status in Cb | |
| EE3A | 30 F4 | BMI $EE30 | loop if the serial clock is low | |
| EE3C | 10 18 | BPL $EE56 | else go set 8 bits to do, branch always | |
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timer A timed out
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| EE3E | A5 A5 | LDA $A5 | get the serial bus bit count | |
| EE40 | F0 05 | BEQ $EE47 | if not already EOI then go flag EOI | |
| EE42 | A9 02 | LDA #$02 | else error $02, read timeour | |
| EE44 | 4C B2 ED | JMP $EDB2 | set the serial status and exit | |
| EE47 | 20 A0 EE | JSR $EEA0 | set the serial data out low | |
| EE4A | 20 85 EE | JSR $EE85 | set the serial clock out high | |
| EE4D | A9 40 | LDA #$40 | set EOI | |
| EE4F | 20 1C FE | JSR $FE1C | OR into the serial status byte | |
| EE52 | E6 A5 | INC $A5 | increment the serial bus bit count, do error on the next timeout | |
| EE54 | D0 CA | BNE $EE20 | go try again, branch always | |
| EE56 | A9 08 | LDA #$08 | set 8 bits to do | |
| EE58 | 85 A5 | STA $A5 | save the serial bus bit count | |
| EE5A | AD 00 DD | LDA $DD00 | read VIA 2 DRA, serial port and video address | |
| EE5D | CD 00 DD | CMP $DD00 | compare it with itself | |
| EE60 | D0 F8 | BNE $EE5A | if changing go try again | |
| EE62 | 0A | ASL A | shift the serial data into the carry | |
| EE63 | 10 F5 | BPL $EE5A | loop while the serial clock is low | |
| EE65 | 66 A4 | ROR $A4 | shift the data bit into the receive byte | |
| EE67 | AD 00 DD | LDA $DD00 | read VIA 2 DRA, serial port and video address | |
| EE6A | CD 00 DD | CMP $DD00 | compare it with itself | |
| EE6D | D0 F8 | BNE $EE67 | if changing go try again | |
| EE6F | 0A | ASL A | shift the serial data into the carry | |
| EE70 | 30 F5 | BMI $EE67 | loop while the serial clock is high | |
| EE72 | C6 A5 | DEC $A5 | decrement the serial bus bit count | |
| EE74 | D0 E4 | BNE $EE5A | loop if not all done | |
| EE76 | 20 A0 EE | JSR $EEA0 | set the serial data out low | |
| EE79 | 24 90 | BIT $90 | test the serial status byte | |
| EE7B | 50 03 | BVC $EE80 | if EOI not set skip the bus end sequence | |
| EE7D | 20 06 EE | JSR $EE06 | 1ms delay, clock high then data high | |
| EE80 | A5 A4 | LDA $A4 | get the receive byte | |
| EE82 | 58 | CLI | enable the interrupts | |
| EE83 | 18 | CLC | flag ok | |
| EE84 | 60 | RTS | ||
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