* DISK BOOT FOR SK*DOS

* DISK CONTROLLER EQUATES

DLATCH  EQU    $E014     DRIVE SELECT LATCH
CMDREG  EQU    $E018     FDC COMMAND REGISTER
STAREG  EQU    CMDREG    FDC STATUS REGISTER
TRKREG  EQU    CMDREG+1  FDC TRACK REGISTER
SECREG  EQU    CMDREG+2  FDC SECTOR REGISTER
DATREG  EQU    CMDREG+3  FDC DATA REGISTER

* ACTUAL BOOT PROGRAM FOLLOWS

FLBOOT  LDS    #$DFBF    RESET STACK
        LDA    #$D0      FORCE INTERRUPT/RESET COMMAND
        STA    CMDREG
        CLR    DLATCH    DRIVE = 0 AND MOTOR ON
        LDB    #3
FLWAIT  LEAX   -1,X      WAIT A BIT FOR MOTORS
        BNE    FLWAIT
FLWAI1  LEAX   -1,X
        BNE    FLWAI1
FLWAI2  LEAX   -1,X
        BNE    FLWAI2
        LDA    #$0F      RESTORE, LOAD, VERIFY, SLOW
        STA    CMDREG
        BSR    SHORTD
FL1     LDB    STAREG    LOOK AT FDC STATUS
        ANDB   #$01      BUSY BIT
        BNE    FL1       WAIT IF STILL BUSY
        LDB    #1
        STB    SECREG    READY FOR TRACK 0 SECTOR 1
        BSR    SHORTD
        LDA    #$8C      READ SECTOR COMMAND
        STA    CMDREG
        BSR    SHORTD
        LDX    #$C100    POINT TO MEMORY
        BRA    CHEKST    GO WAIT FOR DATA
GTDATA  ANDB   #$02      CHECK DRQ BIT
        BEQ    CHEKST    NO DRQ, GET STATUS AGAIN
        LDA    DATREG    DRQ, SO GET DATA
        STA    0,X+      AND STORE INTO MEMORY
CHEKST  LDB    STAREG    CHECK STATUS
        BITB   #$01      BUSY BIT
        BNE    GTDATA    IF STILL BUSY LOOK FOR DATA
        BITB   #$2C      IF NOT BUSY CHECK CRC OR LD
        BEQ    FLDONE    DONE WHEN NO ERROR
        BRA    FLBOOT    REPEAT ON ERROR
FLDONE  JMP    $C100     GO TO EXECUTE SUPER-BOOT

* SHORT DELAY FOR FDC TO SETTLE
SHORTD  LDB    #20
SHORT1  DECB
        BNE    SHORT1
        RTS

        END    FLBOOT