SVIO.DOC

SVIO.DOC - Diskserver I/O documentation

;161002 Added Universal Eprom prog from SRVEPR. L
;161002 Re-entered from old print-out. L
;280786 Modified EPROM-prog. G
;210786 Updated. G
;050486	Created. G

I/O ports

00-03:	Bootrom [0000..1FFF] enable/disable		Write-only
	d0:	0=rom disabled
		1=rom enabled

04-07:	Direct Memory Access controller (Z80-DMA)	Read/Write
	The READY-line is connected to the bus.

08-0B:	Timing controller (Z80-CTC)			Read/Write
	The controller is used for timing,
	and for converting the bus' INTx lines
	to Z80 interrupts.

0C-0F:	?

10-13:	Floppy disk controller extra port		Read/Write
	Extra port to control FDC functions
	normally not controllable by software.

	Write layout is:
	d0-2:	Drive select. Drives avail:
		0-3:	n.a.
		4:	RX01 8' drive (L)
		5:	RX01 8' drive (R)
		6-7:	n.a.
	d3:	Side select (0=side 0).
	d4:	Precomp enable (1 = on).
	d5:	Size. 0=5' drive, 1=8'.
	d6:	Density. 0=double, 1=single.
	d7:	n.c.

	Read layout reflects drive ready status:
	d0: drive 0.
	d1: drive 1.
	...
	d7: drive 7.

14-17:	Floppy controller (MB8877 = 1791)		Read/Write

18-1B:	Configuration switch				Read-only
	d0-7:	reflects switches 0=off
				  1=on

1C-1F:	Prog Comm Interf (8251)				Read/Write
	Baud rate is hard-wired to 9600 bd.

E0-E3:	Eprom programmer for 2764			Read/Write
	The eprom programmer is controlled
	by a 8255 PPI. Current layout:

E0:	Port A. Connected to the databus
	of the 2764.

E1:	Port B. Connected to the addrbus
	[A0-A7] of the 2764.

E2:	Port C. Databits [0..4] connected
	to [A8-A12] of the 2764.
	d5:	Connected to CE of the 2764.
	d6:	Connected to OE of the 2764.
	d7:	Connected to PGM of the 2764.
	CE line is inverted, because writing the
	controlreg of the 8255 clears port C,
	causing unintended programming.

E4-E7:	CRT controller (6845)				Write-only
	Char rate is 1.845 Mhz.
	Display memory is mapped @ [F000-F7FF].
	b7 of video memory causes inverse video.
	It is recommended to use a blinking cursor,
	if any at all.
	If MA13=1, video-memory is not affected.

EC-F7:	Universal Eprom programmer
	The programmer is controlled by
	one 8253 PIT and two 8255 PPIs.

EC-EF:	Universal Eprom programmer PIT (8253)		Read/Write
	Current layout:

EC:	Counter 0. Output connected to PGM\
	of the Eprom; input runs at 1Mhz.

ED:	Counter 1.

EF:	Counter 2. Input runs at 1Mhz.

F0-F3:	Universal Eprom programmer PPI B (8251)		Read/Write
	Current layout:

F0:	PPI B port A. Connected to the
	addrbus [A0-A7] of the Eprom.

F1:	PPI B port B. Connected to the
	addrbus [A8-A15] of the Eprom.

F2:	PPI B port C. Connected to the
	databus [D0-D7] of the Eprom.

F4-F7:	Universal Epromp programmer PPI A (8251)	Read/Write
	Current layout:

F4:	PPI A port A. Eprom pin selection.
	d0:	Selects pin 26 of the Eprom (0=VCC 1=A13)
	d1:	Selects pin 23 of the Eprom (0=VPP 1=A11)
	d2:	Selects pin 1 of the Eprom (0=VPP 1=A15)
	d3:	Selects pin 22 of the Eprom (0=VPP 1=OE/)
	d4:	Selects pin 27 of the Eprom (0=PGM/ 1=A14)
	d5:	Selects pin 20 of the Eprom (0=PGM/ 1=CE/)
	d6:	?
	d7:	?

F5:	PPI A port B. Eprom and programmer control bits.
	d0:	Connected to CE/ of the Eprom.
	d1:	Connected to OE/ of the Eprom.
	d2:	Red led (0=off)
	d3:	Green led (0=off)
	d4:	VCC enable (0=on)
	d5:	VPP enable (0=on)
	d6:	?
	d7:	?

F6:	PPI A port C. Safety and voltage select.
	d0:	Safety (0=disable programming)
	d1:	VCC select (0=5V 1=6V)
	d2-3:	VPP select (00=5V 01=12V 10=21V 11=25V)
	d4:	Connected to PIT output 0.
	d5:	Connected to PIT output 2.
	d6:	?
	d7:	?