0000-                  4
0000-                  5       * ----------------------------------------------------------------------
0000-                  6       * PLAY A SINGLE NOTE USING TIMER1 ON 6522 (VIA) FOUND ON THE PROJECT
0000-                  7       * BOARD. REQUIRES INTERRUPT VECTOR CONFIGURED TO POINT TO INTR (SEE
0000-                  8       * LISTING).
0000-                  9       *
00D0-                 10       VOLUME  .EQ     $D0
00D1-                 11       TEMP    .EQ     $D1
00D2-                 12       OUTPUT  .EQ     $D2
0000-                 13
0000-                 14
00FB-                 15       POINTH  .EQ     $FB         DIGITS 1-2
00FA-                 16       POINTL  .EQ     $FA         DIGITS 3-4
00F9-                 17       INH     .EQ     $F9         DIGITS 5-6
1F1F-                 18       SCANDS  .EQ     $1F1F
0000-                 19
1700-                 20       VIA     .EQ     $1700
1700-                 21       IRB     .EQ     VIA
1700-                 22       ORA     .EQ     VIA + $1
1700-                 23       DDRB    .EQ     VIA + $2
1700-                 24       DDRA    .EQ     VIA + $3
1700-                 25       T1CL    .EQ     VIA + $4
1700-                 26       T1CH    .EQ     VIA + $5
1700-                 27       ACR     .EQ     VIA + $B
1700-                 28       IER     .EQ     VIA + $E
0000-                 29
0200-                 30               .OR     $0200
0200-                 31               .TA     $0200
0200-                 32
0200-A9 FF            33 (  2) SETUP   LDA     #$FF        SET PORT A
0202-8D 00 17         34 (  4)         STA     DDRA         AS OUTPUTS
0205-A9 00            35 (  2)         LDA     #$00        SET PORT B
0207-8D 00 17         36 (  4)         STA     DDRB         AS INPUTS
020A-A9 FF            37 (  2) TIMER   LDA     #$FF        RESET TIMER1
020C-8D 00 17         38 (  4)         STA     T1CL
020F-8D 00 17         39 (  4)         STA     T1CH
0212-A9 40            40 (  2)         LDA     #$40        FREE-RUN MODE WITHOUT
0214-8D 00 17         41 (  4)         STA     ACR          ENABLING OUTPUT ON PB7
0217-A9 C0            42 (  2)         LDA     #$C0        ENABLE VIA
0219-8D 00 17         43 (  4)         STA     IER          INTERRUPT
021C-58               44 (  2)         CLI                 ENABLE CPU INTERRUPT
021D-                 45
021D-A9 FF            46 (  2) WAIT    LDA     #$FF        READ SWITCHES,
021F-4D 00 17         47 (  4)         EOR     IRB          BUT INVERT LOGIC
0222-85 D0            48 (  2)         STA     VOLUME       TO AVOID KEEPING
0224-4C 1D 02         49 (  3)         JMP     WAIT         VOLUME AT 100%
0227-                 50
0227-A9 E4            51 (  2) SETNOTE LDA     #$E4
0229-8D 00 17         52 (  4)         STA     T1CL
022C-A9 17            53 (  2)         LDA     #$17
022E-8D 00 17         54 (  4)         STA     T1CH
0231-60               55 (  6)         RTS
0232-                 56
0232-2C 00 17         57 (  4) INTR    BIT     T1CL
0235-A5 D0            58 (  3)         LDA     VOLUME
0237-C5 D1            59 (  3)         CMP     TEMP
0239-F0 04            60 (2**)         BEQ     TOGGLE
023B-85 D1            61 (  2)         STA     TEMP
023D-85 D2            62 (  2)         STA     OUTPUT
023F-A9 FF            63 (  2) TOGGLE  LDA     #$FF
0241-45 D2            64 (  3)         EOR     OUTPUT
0243-85 D2            65 (  2)         STA     OUTPUT
0245-8D 00 17         66 (  4)         STA     ORA
0248-58               67 (  2)         CLI
0249-40               68 (  6)         RTI