;***************************************
;***************************************
;
; DOS INTERFACE TO THE DISK
;         CONTROLLER
;
;***************************************
;
HDSTRT ;START A NEW IO ENTRANCE
HDCHK ;CHECK ON THE OUTSTANDING IO'S
 LDA IRQMOD ;CHECK IF IRQ MODE
 BNE IRQPRC ;BR IF IRQ MODE
;
; IN BG MODE SO JUST CALL CU
;
 JMP START ;GO TO THE CU
 ;SAME AS 'JSR RTS'
;
; IN IRQ MODE SO SET IRQ REQUEST SWITCH
; AND GO BACK TO BG DISABLED
;
IRQPRC
 STA IRQREQ ;SET THE SWITCH
 TXA ;SAVE X
 PHA ;*
 TYA ;SAVE Y
 PHA ;*
 LDA IEIER ;SAVE ENABLES
 ORA #$80 ;SET THE SET BIT
 PHA ;*
 LDA DRCA ;SAVE ATN ENABLES
 PHA ;*
 LDA #$7F ;DISABLE ALL VIA INTS
 STA IEIER ;*
 LDA #$06 ;DISABLE ATN INTS
 STA DRCA ;*
 JSR IRQEX ;EXIT
 PLA ;RESTORE ATN ENABLES
 STA DRCA ;*
 PLA ;RESTORE VIA ENABLES
 STA IEIER
 PLA ;RESTORE Y
 TAY ;*
 PLA ;RESTORE X
 TAX ;*
 LDA #0 ;CLEAR THE IRQ REQUEST SW.
 STA IRQREQ ;*
 RTS ;EXIT TO CALLER
;
;
;
 .END
