+
−         NAM    mach_coco
+
−         TTL    CoCo machine routines
+
−
+
−         SECTION code
+
−
+
−PIA0Base equ   $FF00
+
−PIA1Base equ   $FF20
+
−
+
−mach_init:
+
−* CoCo 1/2 Initialization Code
+
−         ldx   #PIA1Base               PIA1
+
−         clr   -3,x                    clear PIA0 Control Register A
+
−         clr   -1,x                    clear PIA0 Control Register B
+
−         clr   -4,x                    set PIA0 side A to input
+
−         ldd   #$FF34
+
−         sta   -2,x                    set PIA0 side B to output
+
−         stb   -3,x                    enable PIA0 peripheral reg, disable PIA0
+
−         stb   -1,x                    MPU interrupts, set CA2, CA1 to outputs
+
−         clr   1,x                     $FF20 = DDR, motoroff
+
−         clr   3,x                     $FF22 = DDR, sound disabled
+
−         deca                          A = $FE after deca
+
−         sta   ,x                      bits 1-7 are outputs, bit 0 is input on PIA1 side A
+
−         lda   #$F8
+
−         sta   2,x                     bits 0-2 are inputs, bits 3-7 are outputs on B side
+
−         stb   1,x                     enable peripheral registers, disable PIA1 MPU
+
−         stb   3,x                     interrupts and set CA2, CB2 as outputs
+
−         clr   2,x                     set 6847 mode to alphanumeric
+
−         ldb   #$02
+
−         stb   ,x                      make RS-232 output marking
+
−         clrb
+
−         tfr   b,dp                    B = 0
+
−         ldb   #$04
+
−         clr   -2,x
+
−         bitb  2,x
+
−
+
−         lda   #$37
+
−         sta   PIA1Base+3
+
−
+
−         lda   PIA0Base+3
+
−         ora   #$01
+
−         sta   PIA0Base+3
+
−
+
−         lda   PIA1Base+2
+
−         anda  #$07
+
−         sta   PIA1Base+2
+
−
+
−* 64K DRAM (M0=0, M1=1)
+
−         sta   $FFDA                   RESET M0
+
−         sta   $FFDD                   SET   M1
+
−
+
−         rts
+
−         
+
−         ENDSECT