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41 lines
3.3 KiB
Plaintext
41 lines
3.3 KiB
Plaintext
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0400- I 4 ; 'GETKEY' KEYBOARD INPUT ROUTINE READS AND DEBOUNCES KEYBOARD. RETURNS WITH
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0400- I 5 ; KEY NUMBER IN ACCUMULATOR IF KEY DOWN. OPERATION: SENDS NUMBERS 0-F TO 74154
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0400- I 6 ; (4 TO 16 LINE DECODER), WHICH GROUNDS ONE SIDE OF KEYSWITCHES ONE AT A TIME.
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0400- I 7 ; IF A KEY IS DOWN, PA7 OF VIA #3 WILL BE GROUNDED, AND THE CURRENT VALUE
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0400- I 8 ; APPLIED TO THE 74154 BE THE KEY NUMBER. WHEN THE PROGRAM DETECTS A KEY CLOSE
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0400- I 9 ; CHECKS FOR KEY CLOSURE FOR 50 MS. TO ELIMINATE BOUNCE.
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0400- I 10 ; NOTE: IF NO KEY IS PRESSED, GETKEY WILL WAIT.
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0400- I 11 ;
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0400- I 12 .OR $0400 ; NOTE: BOOK PLACES $0100 INSIDE STACK, BUT WE HAVE
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0400- I 13 .TA $0400 ; MORE MEMORY SO WE ASSEMBLE AT 0400 INSTEAD.
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0400- I 14
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CC03- I 15 DDR3A .EQ $CC03 ; USING RC-ONE ADDRESS DECODING SCHEME, PLACING
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CC02- I 16 DDR3B .EQ $CC02 ; VIA3 AT $CC00 BY DEFAULT (INSTEAD OF $AC00)
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CC01- I 17 PORT3A .EQ $CC01 ; TO FIT RC-ONE ADDRESS DECODING THOUGH ORIGINAL
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CC00- I 18 PORT3B .EQ $CC00 ; CAN BE JUMPERED IF NEEDED/WANTED.
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0400- I 19
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0400-A9 00 I 20 ( 2) LDA #0
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0402-8D 03 CC I 21 ( 4) STA DDR3A ; SET KEY STROBE PORT FOR INPUT
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0405-A9 FF I 22 ( 2) LDA #$FF
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0407-8D 02 CC I 23 ( 4) STA DDR3B ; SET KEYS FOR OUTPUT
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040A-2C 01 CC I 24 ( 4) START BIT PORT3A ; SEE IF KEY IS STILL DOWN FROM LAST KEY CLOSURE:
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040D- I 25 ; KEYSTROBE IN 'N' STATUS BIT.
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040D-10 FB I 26 (2**) BPL START ; IF YES, WAIT FOR KEY RELEASE
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040F-A2 0F I 27 ( 2) RSTART LDX #15 ; SET KEY COUNTER TO 15
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0411-8E 00 CC I 28 ( 4) NXTKEY STX PORT3B ; OUTPUT KEY # TO 74154
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0414-2C 01 CC I 29 ( 4) BIT PORT3A ; SEE IF KEY DOWN: STROBE IN 'N'
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0417-10 05 I 30 (2**) BPL BOUNCE ; IF YES, GO DEBOUNCE
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0419-CA I 31 ( 2) DEX ; DECREMENT KEY #
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041A-10 F5 I 32 (2**) BPL NXTKEY ; NO, DO NEXT KEY
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041C-30 F1 I 33 (2**) BMI RSTART ; START OVER
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041E-8A I 34 ( 2) BOUNCE TXA ; SAVE KEY NUMBER IN A
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041F-A0 12 I 35 ( 2) LDY #$12 ; OUTER LOOP CNT LOAD FOR DELAY OF 50 MS.
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0421-A2 FF I 36 ( 2) LP1 LDX #$FF ; INNER 11 US. LOOP
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0423-2C 01 CC I 37 ( 4) LP2 BIT PORT3A ; SEE IF KEY STILL DOWN
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0426-30 E7 I 38 (2**) BMI RSTART ; IF NOT, KEY NOT VALID, RESTART
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0428-CA I 39 ( 2) DEX
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0429-D0 F8 I 40 (2**) BNE LP2 ; THIS LOOP USES 2115*5 US.
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042B-88 I 41 ( 2) DEY
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042C-D0 F3 I 42 (2**) BNE LP1 ; OUTER LOOP: TOTAL IS 50 MS.
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042E-60 I 43 ( 6) RTS ; DONE: KEY IN A.
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