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