--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/level2/modules/ramd_coco3fpga.asm	Mon Feb 06 22:25:15 2017 +0100
@@ -0,0 +1,217 @@
+********************************************************************
+* RAMD SDRAM Disk Driver for CoCo3FPGA
+*
+* $Id: ramd.asm,v 1.0 2016/12/09 14:52:42 gbecker Exp $
+*
+* Ed.    Comments                                       Who YY/MM/DD
+* ------------------------------------------------------------------
+*  1     Initial driver                         Gary Becker 16/12/09
+*
+*  2     Updated to conform to NitrOS9 Repo     Bill Pierce 17/02/04
+*
+
+*   $FF84: SDRAM Control Register (Write)
+RAMDCON	equ	$00
+* Bit  Signal
+* 0    R/W
+*
+*   $FF84: Disk Flag (Read)
+RAMDSTA	equ	$00
+* Bit  Signal
+*  7   Operation Finished
+*  0   R/W
+*   $FF85-$FF86: DATA (Read / Write)
+RAMDDAT	equ	$01
+*
+*   $FF87-88: Block Address
+RAMDADD	equ	$03
+*
+N.Drives	equ	1	number of drives to support
+*
+* Command equates
+*
+*
+	nam	RAMD
+	ttl	os9 device driver
+
+	use	os9.d
+	use	rbf.d
+	use	coco.d
+
+tylg	set	Drivr+Objct
+atrv	set	ReEnt+rev
+rev	set	$01
+
+	org	0
+	mod	eom,name,tylg,atrv,start,size
+	fcb	$ff
+
+u0000	rmb	DRVBEG+(DRVMEM*N.Drives)
+
+size	equ	.
+
+	fcb	$FF		This byte is the driver permissions
+name	fcs	/RAMD/
+	fcb	1		edition #1
+
+start	bra	INIT		3 bytes per entry to keep RBF happy
+	nop
+	bra	READ
+	nop
+	bra	WRITE
+	nop
+	bra	GETSTA
+	nop
+	bra	SETSTA
+	nop
+	bra	TERM
+	nop
+
+* Read
+*
+* Entry:
+*	B = MSB of LSN
+*	X = LSB of LSN
+*	Y = address of path descriptor
+*	U = address of device memory area
+*
+* Exit:
+*	CC = carry set on error
+*	B = error code
+*
+READ	lda	#$01		1=READ the sector
+	tstb			Make sure 3rd byte of LSN is 0
+	bne	ERROR
+	pshs	x,y		Save these registers for later
+	tst	,s		Check high bit of X (Low 16 bits of LSN)
+	bmi	ERROR2		Should equal 0
+	bsr	GetSect		Go read the sector
+	puls	x,y
+	tfr	x,d
+	tstb			Test one byte of saved X
+	bne	TERM
+	tsta			Test other byte of saved X
+	bne	TERM
+* LSN0, standard OS-9 format
+	ldy	PD.BUF,y	address of buffer
+	leau	DRVBEG,u	point to the beginning of the drive tables
+	ldb	#DD.SIZ		copy bytes over
+copy.0	lda	,y+		grab from LSN0
+	sta	,u+		save into device static storage
+	decb			Finished when B=0
+	bne	copy.0
+	bra	TERM		Return
+
+*
+* Entry:
+*	B = MSB of LSN
+*	X = LSB of LSN
+*	Y = address of path descriptor
+*	U = address of device memory area
+*
+* Exit:
+*	CC = carry set on error
+*	B = error code
+*
+GetSect
+*	orcc	#IntMasks	Kill interrupts
+	pshs	x		save 2 byte LSN
+	ldx	V.PORT,u	get address of hardware
+	sta	RAMDCON,x	Setup for a READ
+	puls	d		Get 2 byte LSN
+	std	RAMDADD,x	Put it in the address
+	ldy	PD.BUF,y	address of buffer 
+	lda	#$80		128 2 byte transfers
+	pshs	a		On stack
+	lda	RAMDDAT+1,x	Start transfer
+LP0	tst	RAMDSTA,x	Is transfer completed?
+	bpl	LP0
+	ldd	RAMDDAT,x	Yes, read 2 bytes from RAM
+	std	,y++		Store them in buffer
+	dec	,s		Are we finished?
+	bne	LP0		No
+	puls	b		clear b
+*	andcc	#^(IntMasks)	Renable Interrupts
+	rts
+
+ERROR2	puls	x,y
+ERROR	ldb	E$SeekRg	Only error is Seek out of Range
+	comb			Set carry bit
+	rts
+
+* Init
+*
+* Entry:
+*	Y = address of device descriptor
+*	U = address of device memory area
+*
+* Exit:
+*	CC = carry set on error
+*	B = error code
+*	
+INIT
+	leax	DRVBEG,u	point to the beginning of the drive tables
+	ldd	#$8000		Number of total sectors
+	stb	DD.TOT,x	$00
+	std	DD.TOT+1,x	$8000
+	ldd	#$0100		A=$01 B=$00
+	stb	V.NDRV,u	$01
+*	lda	#$FF		Probably not needed
+*	sta	V.TRAK,u
+	
+TERM
+* no SetSta calls - return, no error, ignore
+SETSTA
+* no GetSta calls - return, no error, ignore
+GETSTA
+	andcc #^Carry		clear carry
+	 rts
+
+*
+* Entry:
+*	B = MSB of LSN
+*	X = LSB of LSN
+*	Y = address of path descriptor
+*	U = address of device memory area
+*
+* Exit:
+*	CC = carry set on error
+*	B = error code
+*
+WRITE	clra			0 =WRITE to disk
+	tstb			Make sure 3rd byte of LSN is 0
+	bne			ERROR
+	pshs	x,y		Save these registers for later
+	tst	,s		Check high bit of X (Low 16 bits of LSN)
+	bmi	ERROR2		Should equal 0
+* Get Sector comes here with:
+* Entry: A = read/write command code (0/1)
+*	B = MSB of the disk's LSN
+*	X = LSW of the disk's LSN
+*	Y = path dsc. ptr
+*	U = Device static storage ptr
+* Exit:	CC = carry set on error
+*	A = error status from command register
+PutSect
+*	orcc	#IntMasks	Kill interrupts
+	ldx	V.PORT,u	get address of hardware
+	sta	RAMDCON,x	Setup for a READ
+	ldy	PD.BUF,y	address of buffer
+	puls	d		Get 2 byte LSN
+	std	RAMDADD,x	Put it in the address
+	lda	#$80		128 2 byte transfers
+	pshs	a		On stack
+LP2	ldd	,y++		get 2 bytes
+	std	RAMDDAT,x	write them to th RAM
+LP1	tst	RAMDSTA,x	is the transfer completed?
+	bpl	LP1
+	dec	,s
+	bne	LP2
+	puls	b		clear b
+	puls	y
+*	andcc	#^(IntMasks)	Renable Interrupts
+	bra	TERM
+
+	emod
+
+eom	equ	*
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