forked from Apple-2-HW/gp2io
34 lines
5.0 KiB
Plaintext
34 lines
5.0 KiB
Plaintext
------+----------------------+-------------+----+---------+------+-----------------------+-------------------------------------------------------------------
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Line | # File Line | Line Type | MX | Reloc | Size | Address Object Code | Source Code
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------+----------------------+-------------+----+---------+------+-----------------------+-------------------------------------------------------------------
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1 | 1 readbyte.s 1 | Directive | 11 | | 0 | 00/8000 | ORG $34A
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2 | 1 readbyte.s 2 | Equivalence | 11 | | 0 | 00/034A | ANN2HI EQU $C05D
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3 | 1 readbyte.s 3 | Equivalence | 11 | | 0 | 00/034A | ANN2LO EQU $C05C
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4 | 1 readbyte.s 4 | Equivalence | 11 | | 0 | 00/034A | BUTT1 EQU $C062
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5 | 1 readbyte.s 5 | Equivalence | 11 | | 0 | 00/034A | BYTETRCVD EQU $EF
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6 | 1 readbyte.s 6 | Equivalence | 11 | | 0 | 00/034A | BUTT1HILO EQU $EE
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7 | 1 readbyte.s 7 | Empty | 11 | | 0 | 00/034A |
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8 | 1 readbyte.s 8 | Empty | 11 | | 0 | 00/034A |
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9 | 1 readbyte.s 9 | Code | 11 | | 2 | 00/034A : A2 09 | READBYTE LDX #$09 ; reading 8 bits requires 9 transitions.
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10 | 1 readbyte.s 10 | Code | 11 | | 2 | 00/034C : A9 00 | LDA #$00 ; clear the accumulator
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11 | 1 readbyte.s 11 | Code | 11 | | 2 | 00/034E : 85 EF | STA {$EF} ; $EF is staging for received byte, set 0
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12 | 1 readbyte.s 12 | Code | 11 | | 2 | 00/0350 : 85 EE | STA {$EE} ; $EE is staging for each bit, set 0
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13 | 1 readbyte.s 13 | Code | 11 | | 3 | 00/0352 : 8D 5D C0 | CTS STA {$C05D} ; set ANN2 HIGH, indicate to AVR "Clear to Send"
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14 | 1 readbyte.s 14 | Code | 11 | | 2 | 00/0355 : A0 FF | LOOPSTART LDY #$FF ; start wait loop
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15 | 1 readbyte.s 15 | Code | 11 | | 1 | 00/0357 : C8 | LOOPCOUNT INY ; Increment Y - rolls over to 0 on first run (loopcount)
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16 | 1 readbyte.s 16 | Code | 11 | | 3 | 00/0358 : AD 62 C0 | LDA {$C062} ; check PB1 status hi/low
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17 | 1 readbyte.s 17 | Code | 11 | | 2 | 00/035B : 29 80 | AND #$80 ; clear 0-6 bits (just need bit 7, all others float)
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18 | 1 readbyte.s 18 | Code | 11 | | 2 | 00/035D : C5 EE | CMP {$EE} ; compare Accumulator 7 bit with $EE, previous PB2 value
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19 | 1 readbyte.s 19 | Code | 11 | | 2 | 00/035F : D0 02 | BNE BITCHANGE ; if PB2 has changed state, store in $EE (bitchange)
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20 | 1 readbyte.s 20 | Code | 11 | | 2 | 00/0361 : F0 F4 | BEQ LOOPCOUNT ; bit hasn't changed yet, return to (loopcount)
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21 | 1 readbyte.s 21 | Code | 11 | | 2 | 00/0363 : 85 EE | BITCHANGE STA {$EE} ; (bitchange)
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22 | 1 readbyte.s 22 | Code | 11 | | 2 | 00/0365 : C0 44 | CPY #$44 ; if the loop count is more than 68, bit is one. Bit is set in Carry
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23 | 1 readbyte.s 23 | Code | 11 | | 2 | 00/0367 : 26 EF | ROL {$EF} ; rotate the new bit into $EF, our result byte.
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24 | 1 readbyte.s 24 | Code | 11 | | 1 | 00/0369 : CA | DEX ; decrement X, our bit count
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25 | 1 readbyte.s 25 | Code | 11 | | 2 | 00/036A : D0 E9 | BNE LOOPSTART ; if bit count is not yet full, loop back to (loopcount)
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26 | 1 readbyte.s 26 | Code | 11 | | 3 | 00/036C : 8D 5C C0 | CTSOFF STA {$C05C} ; if bit count is full, set ANN2 LOW, CTS off
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27 | 1 readbyte.s 27 | Code | 11 | | 2 | 00/036F : A5 EF | LDA {$EF} ; puts received byte into Accumulator
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28 | 1 readbyte.s 28 | Code | 11 | | 1 | 00/0371 : 60 | RTS ; return with byte in Accumulator
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29 | 1 readbyte.s 29 | Empty | 11 | | 0 | 00/0372 |
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------+----------------------+-------------+----+---------+------+-----------------------+-------------------------------------------------------------------
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