* Parallel Printer device for Dragon 32/64/Alpha.
*
* Disassembled from the Alpha OS-9 2005-06-14, P.Harvey-Smith.
*

	nam   scdpp
        ttl   Dragon Parallel Printer Driver 

* Disassembled 1900/00/00 00:08:11 by Disasm v1.5 (C) 1988 by RML

        ifp1
        use   	defsfile
        endc

tylg    set   	Drivr+Objct   
atrv    set   	ReEnt+rev
rev     set   	$01
edition set	3
        mod   	eom,name,tylg,atrv,start,size

u0000   rmb   29
size    equ   .

	fcb	$03 
name    equ   	*
        fcs   	/scdpp/
        fcb   	edition
	
start   equ   	*
        lbra  	Init
        lbra  	Read
        lbra  	Write
        lbra  	GetStat
        lbra  	SetStat
        lbra  	Term

* Init
*
* Entry:
*    Y  = address of device descriptor
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*
Init   	pshs  	cc
        orcc  	#$50		; Disable Inturrupts
        ldx   	#PIA1DA		; Point to PIA1DA
        ldb   	1,x		; Get CRA
        clr   	1,x		; Zero CR and select DDRA
        lda   	#$FE		; Set bit 0 as input (cassette in), all others as input
        sta   	,x
        stb   	1,x		; Restore CRA
        ldx   	#PIA1DB		; Point at PIA1DB
        ldb   	1,x		; Save CRB
        clr   	1,x		; Zero CR and select DDRB
        lda   	,x		; get DDRB
        anda  	#$FE		; Set bit 0 as input (printer busy), all others leave alone
        sta   	,x		
        stb   	1,x		; restore CRB
        puls  	cc
        clrb  			; Flag no error
        rts

* Read
*
* Entry:
*    B  = MSB of the disk's LSN
*    X  = LSB of the disk's LSN
*    Y  = address of path descriptor
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*

Read   	ldb   	#$CB		; Ilegal mode, cannot read from printer !
        orcc  	#$01
        rts   
	
* Write
*
* Entry:
*    B  = MSB of the disk's LSN
*    X  = LSB of the disk's LSN
*    Y  = address of path descriptor
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*

Write   pshs  	a
L0053   ldb   	#$08		; retry count
L0055   lda   	>PIA1DB		; Get printer busy flag
        lsra  			; Get busy bit into carry
        bcc   	WriteNotBusy		; Not busy : continue
        nop   			; wait a little while
        nop   
        decb  			; decrement retry counter
        bne   	L0055		; Non zero : check flag again
	
        pshs  	x		; Still busy: send calling process to sleep
        ldx   	#$0001
        os9   	F$Sleep  
        puls  	x
        bra   	L0053		; When we wake, poll busy again
	
WriteNotBusy   
	puls  	a
        pshs  	cc		
        orcc  	#$50		; disable inturrupts
        sta   	>PIA0DB		; Send character to printer
        lda   	>PIA1DA		; Toggle printer strobe line
        ora   	#$02		; high
        sta   	>PIA1DA		
        anda  	#$FD		; and low again
        sta   	>PIA1DA
        puls  	pc,cc		; restore and return
	
* GetStat
*
* Entry:
*    A  = function code
*    Y  = address of path descriptor
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*
GetStat   
	cmpa  	#$01
        bne   	L008A
L0088   clrb  
        rts 
	
L008A   cmpa  	#$06
        beq   	L0088
*
* SetStat
*
* Entry:
*    A  = function code
*    Y  = address of path descriptor
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*
SetStat   
	comb  
        ldb   	#$D0
        rts
*
* Term
*
* Entry:
*    U  = address of device memory area
*
* Exit:
*    CC = carry set on error
*    B  = error code
*

Term   	rts

        emod
eom     equ   *
        end