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2163
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1 NAM mach_coco
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2 TTL CoCo machine routines
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3
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4 PSECT mach_coco,0,0,0,0,mach_init
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5
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6 VSECT
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7 ENDSECT
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8
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9 PIA0Base equ $FF00
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10 PIA1Base equ $FF20
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11
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12 mach_init:
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13 * CoCo 1/2 Initialization Code
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14 ldx #PIA1Base PIA1
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15 clr -3,x clear PIA0 Control Register A
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16 clr -1,x clear PIA0 Control Register B
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17 clr -4,x set PIA0 side A to input
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18 ldd #$FF34
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19 sta -2,x set PIA0 side B to output
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20 stb -3,x enable PIA0 peripheral reg, disable PIA0
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21 stb -1,x MPU interrupts, set CA2, CA1 to outputs
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22 clr 1,x $FF20 = DDR, motoroff
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23 clr 3,x $FF22 = DDR, sound disabled
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24 deca A = $FE after deca
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25 sta ,x bits 1-7 are outputs, bit 0 is input on PIA1 side A
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26 lda #$F8
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27 sta 2,x bits 0-2 are inputs, bits 3-7 are outputs on B side
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28 stb 1,x enable peripheral registers, disable PIA1 MPU
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29 stb 3,x interrupts and set CA2, CB2 as outputs
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30 clr 2,x set 6847 mode to alphanumeric
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31 ldb #$02
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32 stb ,x make RS-232 output marking
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33 clrb
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34 tfr b,dp B = 0
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35 ldb #$04
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36 clr -2,x
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37 bitb 2,x
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38
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39 lda #$37
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40 sta PIA1Base+3
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41
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42 lda PIA0Base+3
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43 ora #$01
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44 sta PIA0Base+3
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45
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46 lda PIA1Base+2
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47 anda #$07
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48 sta PIA1Base+2
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49
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50 * 64K DRAM (M0=0, M1=1)
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51 sta $FFDA RESET M0
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52 sta $FFDD SET M1
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53
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54 rts
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55
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56 endsect
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