Simple SCSI interfaces for Z80 boards
Michael Joosten
looking through my scrap cardboxes I came again across two old OMTI 5400
controllers (SASI to FDD/ST506/QIC02) and a nice Z80 board, probably
from an ATM, with CTC,SIO/0, three PIOs and and extension board with an
additional set of 3 PIOs and a DART.
So, I said to myself, why not try to simply use one PIO or a little
discrete circuitry (latches etc) to form a SASI port, take a BIOS and
even a boot monitor that already suited for such an interface and make
my own little CP/M board.
So far, I've seen the schematics for BigBoard II which had such a simple
SASI port from just a few TTLs. There also exists somebody who thinks he
still has the VARBIOS for this beast, which had an expansion option to
use a XEBEC SASI controller to drive a ST506 disk. A similar interface
has been documented at http://www.6502.org/users/andre/scsi/index.html.
Then, there are traces in the net of Ampro's LittleBoard and a SCSI
daughter board that used a NCR 5380. Here, an option could be an old HP
scanner SCSI ISA 8bit card with a 53C400. (Or find somebody who throws
away an old SCSI ISA board with a 5380). A suitable BIOS seems to be
also available.
Next, I've seen that the Heathkit H89 also had a SASI option, and that
Mr. Wilkerson has the full BIOS of this beast, which even includes the
option to use a 8" floppy along with a hard disk via SASI. But I don't
know about the hardware...
And somebody promised me the docs for the OMTI (still need to remind
him, though). So...
Can somebody give me some idea how the H89 SASI interface looks like?
My main intention is to 'escape' from making my own boards and solder
work as much as possible. Not that I don't know how to hold a soldering
iron, but wire-wrapping, layout, and tinkering with fine wires whose
isolation is surprisingly stubborn is not anymore to my taste...
Can anybody recommend a nice monitor program to start with?
Of course, I have zero docs for that board. There is a slot with a
battery-backed CMOS RAM card of 64kB, apparently in parallel with two
sockets for a 27256 (EPROM) and a 43256 (SRAM). Unfortunately, I would
have to implement a little bankswitching on my own, at least to disable
the EPROM after /RESET. Reengineering schematics from a PCB is boring
work...
--
Michael Joosten, SBS C-LAB, jo...@c-lab.de
Fuerstenallee 11, 33094 Paderborn, Germany
Phone: +49 5251 606127, Fax: +49 5251 606065
C-LAB is a cooperation of University Paderborn & SIEMENS
Lee Hart
> I came across two old OMTI 5400 controllers (SASI to FDD/ST506/QIC02)
> and a nice Z80 board, probably from an ATM, with CTC,SIO/0, three PIOs
> and and extension board with an additional set of 3 PIOs and a DART.
> So, I said to myself, why not try to simply use one PIO or a little
> discrete circuitry (latches etc) to form a SASI port, take a BIOS and
> even a boot monitor that already suited for such an interface and make
> Next, I've seen that the Heathkit H89 also had a SASI option, and that
> Mr. Wilkerson has the full BIOS of this beast, which even includes the
> option to use a 8" floppy along with a hard disk via SASI. But I don't
> SASI interface looks like?
Heath called their hard drive setup for the H89 the "H67" (or "Z67" if
purchased from Zenith). It was a large cabinet with two full-height 8"
drives (one DSDD 8" floppy, and one 10 megabyte Memorex hard drive), a
DTC controller board, and power supply. A 40-pin ribbon cable connected
it to the H89 computer. This 40-pin cable was essentially the 50-pin
SASI interface (SASI preceeded SCSI), with a couple wires moved to fit
the smaller connector.
Inside the H89, a "host adapter" card interfaces this 50-pin cable to
the CPU board. To the Z80, this host adapter just provided two I/O
ports; Data In/Out at port 78 hex, and Control/Status at port 79 hex.
There was also a DIP switch at port 7A hex, though it was not used.
I have all the manuals for it, including commented source for the boot
ROMs and CP/M 2.2 BIOS, and even a couple of the host adpater boards
themselves from Heath H89s. I'd be happy to send you copies of the
documentation if you pay the cost of postage and copying (about 5 cents
a page).
I'd also sell a host adapter board for $10 plus shipping. It just uses
SSI TTL to implement the I/O ports; nothing at all fancy. It wouldn't
take much to interface it to any Z80.
> My main intention is to 'escape' from making my own boards and solder
> work as much as possible. Not that I don't know how to hold a soldering
> iron, but wire-wrapping, layout, and tinkering with fine wires whose
> isolation is surprisingly stubborn is not anymore to my taste...
>
> Can anybody recommend a nice monitor program to start with?
>
> Of course, I have zero docs for that board. There is a slot with a
> battery-backed CMOS RAM card of 64kB, apparently in parallel with two
> sockets for a 27256 (EPROM) and a 43256 (SRAM). Unfortunately, I would
> have to implement a little bankswitching on my own, at least to disable
> the EPROM after /RESET. Reengineering schematics from a PCB is boring
> work...
--
Lee A. Hart Ring the bells that still can ring
814 8th Ave. N. Forget your perfect offering
Sartell, MN 56377 USA There is a crack in everything
leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
Don Maslin
: Hi,
: looking through my scrap cardboxes I came again across two old OMTI 5400
: controllers (SASI to FDD/ST506/QIC02) and a nice Z80 board, probably
: from an ATM, with CTC,SIO/0, three PIOs and and extension board with an
: additional set of 3 PIOs and a DART.
: So, I said to myself, why not try to simply use one PIO or a little
: discrete circuitry (latches etc) to form a SASI port, take a BIOS and
: even a boot monitor that already suited for such an interface and make
: my own little CP/M board.
: So far, I've seen the schematics for BigBoard II which had such a simple
: SASI port from just a few TTLs. There also exists somebody who thinks he
: still has the VARBIOS for this beast, which had an expansion option to
: use a XEBEC SASI controller to drive a ST506 disk. A similar interface
: has been documented at http://www.6502.org/users/andre/scsi/index.html.
: Then, there are traces in the net of Ampro's LittleBoard and a SCSI
: daughter board that used a NCR 5380. Here, an option could be an old HP
: scanner SCSI ISA 8bit card with a 53C400. (Or find somebody who throws
: away an old SCSI ISA board with a 5380). A suitable BIOS seems to be
: also available.
Another possible source are the older little Macs - SE and such - which
carry a 40-pin DIP 5380 soldered to the board. Later ones were SMT.
- don
: Next, I've seen that the Heathkit H89 also had a SASI option, and that
Frank Zsitvay
Don Maslin wrote:
>
> Michael Joosten <jo...@c-lab.de> wrote:
> : Then, there are traces in the net of Ampro's LittleBoard and a SCSI
> : daughter board that used a NCR 5380. Here, an option could be an old HP
> : scanner SCSI ISA 8bit card with a 53C400. (Or find somebody who throws
> : away an old SCSI ISA board with a 5380). A suitable BIOS seems to be
> : also available.
>
> Another possible source are the older little Macs - SE and such - which
> carry a 40-pin DIP 5380 soldered to the board. Later ones were SMT.
>
> - don
I wonder - wouldn't it be possible to implement a SASI/SCSI
host using a Z80PIO chip? Use port A in Bidirectional mode
and port B in single bit mode, and implement the protocol in
software? It's tailor made for the Z80 bus.
-Frank
Hans Johansson
> Hi,
>
<snip>
> So far, I've seen the schematics for BigBoard II which had such a
> simple SASI port from just a few TTLs. There also exists somebody who
> thinks he still has the VARBIOS for this beast, which had an
> expansion option to use a XEBEC SASI controller to drive a ST506
> disk. A similar interface has been documented at
> http://www.6502.org/users/andre/scsi/index.html.
<snip>
Does naybody here knows where to find technical information about the XEBEC
SASI controller. My computer is equipped with one but I don't yet know (it's
only 20 yrs old..) how to exploit this...
/Hans
Michael Joosten
The BigBoard II VARBIOS should have some more details on this. So far,
I've just this old Elektor Computing Special Magazine, No. 3 from
'85/'86 which has about a page about the XEBEC (hmmm, some diagramm says
XEBEC-S1410). Nothing really detailed, only that the 5th and 6th bytes
of the SCSI CDB contains specific data, the fith the interleave or block
count and the 6ixth uses some bytes for hard-disk specific data, like:
bit0: half step for Seagate/TexasInstruments drives
bit1: half step for Tandon
bit2: 'buffer step' option for Computer Memories/Rotating Memory
drives, stepping pulse every 200us.
bit3:5 not used, zero
bit6: normally 0, if set , sector will be reread after a read error.
bit7: normally 0, controller retries wrires/reads up to four times. No
retries if set
bit0 is the LSB.
The controller returns 2 status bytes, where the second is always 0 and
the first uses bit 1 for error indication, bit 5 to indicate for which
of the two drives (LUNs) the error occured. That's it...
Michael Joosten
>
> I wonder - wouldn't it be possible to implement a SASI/SCSI
> host using a Z80PIO chip? Use port A in Bidirectional mode
> and port B in single bit mode, and implement the protocol in
> software? It's tailor made for the Z80 bus.
>
That's exactly what I'm asking myself...
Michael Joosten
>
>
> Another possible source are the older little Macs - SE and such - which
> carry a 40-pin DIP 5380 soldered to the board. Later ones were SMT.
>
> - don
>
Yes, this is also an alternative, looking for the main board of a broken
Mac.
I also have some old dead hard disk PCBs, with a 53C90 or some dead Sun
ELC/SLC boards, with Emulex 24001XX controllers, which are very similar
to the 53C90 etc. Unfortunately in PLCC...
Michael Joosten
>
> Heath called their hard drive setup for the H89 the "H67" (or "Z67" if
> purchased from Zenith). It was a large cabinet with two full-height 8"
> drives (one DSDD 8" floppy, and one 10 megabyte Memorex hard drive), a
> DTC controller board, and power supply. A 40-pin ribbon cable connected
> it to the H89 computer. This 40-pin cable was essentially the 50-pin
> SASI interface (SASI preceeded SCSI), with a couple wires moved to fit
> the smaller connector.
>
> Inside the H89, a "host adapter" card interfaces this 50-pin cable to
> the CPU board. To the Z80, this host adapter just provided two I/O
> ports; Data In/Out at port 78 hex, and Control/Status at port 79 hex.
> There was also a DIP switch at port 7A hex, though it was not used.
Ah, thanks for the details. Knowing the port addresses makes reading the
BIOS source a little easier, though it's a tricky one: Most of the
addresses are determined in the cold boot/init subroutine and written
into the specific IO subroutines in the byte after the specific IN or
OUT instruction byte....
>
> I have all the manuals for it, including commented source for the boot
> ROMs and CP/M 2.2 BIOS, and even a couple of the host adpater boards
> themselves from Heath H89s. I'd be happy to send you copies of the
> documentation if you pay the cost of postage and copying (about 5 cents
> a page).
To Germany this will be more than just a few cents....
>
> I'd also sell a host adapter board for $10 plus shipping. It just uses
> SSI TTL to implement the I/O ports; nothing at all fancy. It wouldn't
> take much to interface it to any Z80.
>
Mmm, let's see. This looks like the same setup as the BigBoard II uses:
A '373 as output latch with a bunch of 7438 NANDs as gated drivers, a
'240 as input port (SCSI has inverted logic), and two '74, more '38 and
some inverters for the control lines.
Must hurry now, I'll come back next week.
David Chiu
person,) not sure if I still have it. I do remember that the beast (with
unmodified firmware) requires the drive geometry be programmed in before the
attached drives are usable, so using it as boot device may present some
problem. This was when XEBEC were packaging them with Seagate MFM drives and
SASI HBA under FirstClass/Sider label for Apple IIs (how I have aged, badly.)
Harold F. Bower
Frank Zsitvay <fr...@rdwarf.com> wrote:
> I wonder - wouldn't it be possible to implement a SASI/SCSI
> host using a Z80PIO chip? Use port A in Bidirectional mode
> and port B in single bit mode, and implement the protocol in
> software? It's tailor made for the Z80 bus.
There was such an implementation on an S100 Single-board computer, the
ICD XL-M180. Not many were made (from what I understand), but I have
one along with copies of the hand-drawn schematic. The software was
tailored versions of the ZCPR 3 CCP, early ZRDOS (IIRC) and custom
utilities for the special boot process, sysgen, hdinit and others.
Never did much with it because I couldn't stand the slowness of a 6.144
MHz HD64180 with 512 MB of DRAM after experiencing 9-18 MHz Z180s with
static memory :-)
This board was also socketted for an Intel LAN chip, but I don't recall
seeing any S/W for it, and the socket is vacant on my board.
Hal
LGeoCole
that had an SASI interface. Wouldn't be surprised
if you haven't heard of it. It had a wimpy power
supply that may have been its main downfall.
It ran CP/M-3. I used the system disks as a base
for implementing CP/M-3 on my Compupro. Never
tried to get the SASI to work. I have three
that work. Unfortunately, they, their disks,
and their documentation are a hundred miles away.
Don't know when I'll get back to them.
If anyone has a no-hurry interest in information,
I'll put a flag in my to-do list for when I get
back there.
George C.
Peter Hill
wrote:
There is a book on writing device drivers for Unix that takes the
reader though a driver to use the 25 pin parallel port of a PC as a
SCSI port. It is very limited though, about 25cm/10in cable and one
device, due to PC not having the right current drive or sink. The PC
port is just a PIO, needs buffering to the right levels.
--
Peter Hill
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!
Frank Zsitvay
Michael Joosten wrote:
>
> Lee Hart wrote:
> >
> > I have all the manuals for it, including commented source for the boot
> > ROMs and CP/M 2.2 BIOS, and even a couple of the host adpater boards
> > themselves from Heath H89s. I'd be happy to send you copies of the
> > documentation if you pay the cost of postage and copying (about 5 cents
> > a page).
>
> To Germany this will be more than just a few cents....
>
> >
> > I'd also sell a host adapter board for $10 plus shipping. It just uses
> > SSI TTL to implement the I/O ports; nothing at all fancy. It wouldn't
> > take much to interface it to any Z80.
> >
>
> Mmm, let's see. This looks like the same setup as the BigBoard II uses:
> A '373 as output latch with a bunch of 7438 NANDs as gated drivers, a
> '240 as input port (SCSI has inverted logic), and two '74, more '38 and
> some inverters for the control lines.
>
> Must hurry now, I'll come back next week.
You know, guys, scanners are dirt cheap these days. If all
you're doing is sending information, you could scan them into
binary form, compress with your favorite compression format,
and post them on an FTP site somewhere for later transfer in
the middle of the night.
A lot of this older information would be really useful to
have widely available. Given the age and subject matter, I
doubt the copyright police would even bother. And if they
did, then it could be taken down.
-Frank
Lee Hart
> I wonder - wouldn't it be possible to implement a SASI/SCSI
> host using a Z80PIO chip? Use port A in Bidirectional mode
> and port B in single bit mode, and implement the protocol in
> software? It's tailor made for the Z80 bus.
The SASI/SCSI bus uses fairly high current open-collector drivers. The
PIO would required TTL drivers. But as soon as you add the drives, you
have more chips than a NCR5380 or plain TTL implementation would have
required.
Lee Hart
> You know, guys, scanners are dirt cheap these days. If all
> you're doing is sending information, you could scan them into
> binary form, compress with your favorite compression format,
> and post them on an FTP site somewhere for later transfer in
> the middle of the night.
It's not the hardware that's expensive; it's the time to do it. People
aren't willing to pay anything for someone else's time or information.
I'll use the Heath hard drive documentation as an example: You are
talking about 300+ pages of documentation; it would take many hours to
scan it all. The source code listings are already printed half-size to
conserve paper, which means the scanned results may be unreadable.
Besides, what you want is not a photograph of the listing, but a
machine-readable version that you can edit and assemble.
Herbert R Johnson
"Hans Johansson" <hextraanscjoh...@hotmail.com> wrote:
*>Michael Joosten wrote:
*>> Hi,
*>>
*><snip>
*>
*>> So far, I've seen the schematics for BigBoard II which had such a
*>> simple SASI port from just a few TTLs. There also exists somebody who
*>> thinks he still has the VARBIOS for this beast, which had an
*>> expansion option to use a XEBEC SASI controller to drive a ST506
*>> disk. A similar interface has been documented at
*>> http://www.6502.org/users/andre/scsi/index.html.
*>
*><snip>
*>
*>Does naybody here knows where to find technical information about the XEBEC
*>SASI controller. My computer is equipped with one but I don't yet know (it's
*>only 20 yrs old..) how to exploit this...
*>
*>/Hans
Among other kinds of S-100 documentation, I try to maintain some docs on
these older SASI/SCSI controller cards; and I have a few of the cards
as well for sale. Check my Web site at
http://pluto.njcc.com/~hjohnson/s_drives.htm
for what I've got in my archives. I'd certainly welcome more originals or
copies of SASI/SCSI controller cards from the 1980's or so. If anyone
has some of these docs, contact me and we'll discuss terms including
trading "copies for copies", page for page, which is my usual offer.
Otherwise I charge a per-page copy fee and handling costs, which covers
my time, effort, acquisition and storage of these old documents. I'm
not sure if I have the XEBEC doc or not, depending on the model number.
If someone has a Web pointer to such docs, I'll simply add that Web
pointer to my list of S-100 Web pointers. However these days Google
is so convenient that I really don't keep up my list of pointers.
Herb Johnson
Herbert R. Johnson voice 609-771-1503, New Jersey USA
<a href="http://pluto.njcc.com/~hjohnson"> to my web site</a>
Web site: http://pluto.njcc.com/~hjohnson
email address: hjoh...@pluto.njcc.com
amateur astronomer and telescope tinkerer
reseller of classic Macs & accessories from Plus to PowerMac
S-100 & 8-inch drive manuals and parts, call for "Dr. S-100"
--
Herbert R. Johnson http://pluto.njcc.com/~hjohnson
hjoh...@pluto.njcc.com voice 609-771-1503, New Jersey USA
amateur astronomer and telescope tinkerer
reseller of classic Macs & accessories from Plus to PowerMac
S-100 & 8-inch drive manuals and parts, call for "Dr. S-100"
Frank Zsitvay
Herbert R Johnson wrote:
> Among other kinds of S-100 documentation, I try to maintain some docs on
> these older SASI/SCSI controller cards; and I have a few of the cards
> as well for sale. Check my Web site at
>
> http://pluto.njcc.com/~hjohnson/s_drives.htm
For some reason, this link returns a 404 for me. ???
-Frank
Clarence Wilkerson
directly via the Heath SASI interface.
I'll see if I can excavate it.
--
Clarence Wilkerson \ HomePage: http://www.math.purdue.edu/~wilker
Prof. of Math. \ Internet: wil...@math.purdue.edu
Dept. of Mathematics \ Messages: (765) 494-1903, FAX 494-0548
Purdue University, \
W. Lafayette, IN 47907-1395 \
Clarence Wilkerson
There were more alike than differenct in the command structures, even though
it's not quite SCSI.
However, each one seemed to a different method of identifying the hard drive
parameters, ranging from hardcoded in the onboard EPROM to a sector on the
disk with the data written there.
With a lot of tinkering, I was able to make the Heath SASI interface and
BIOS code work with many of these.
antonio.carlini
> It's not the hardware that's expensive; it's the time to do it. People
> aren't willing to pay anything for someone else's time or information.
True :-)
> I'll use the Heath hard drive documentation as an example: You are
> talking about 300+ pages of documentation; it would take many hours to
> scan it all. The source code listings are already printed half-size to
Double-sided US-Letter size might be 30-60 minutes in
a sheet-feed scanner. You might need to attend to it once
or twice if it only takes 50-100 pages in one go. Of course,
if you don't have a scanner with a sheet-feeder, this part
is moot !
> conserve paper, which means the scanned results may be unreadable.
> Besides, what you want is not a photograph of the listing, but a
> machine-readable version that you can edit and assemble.
The OCR part *is* the tough part. The only *good* thing
about OCRing source code is that you can throw the result
through an assembler (or compiler) to catch (most) errors.
That and the font is usually quite good for OCR. OK, so
the *two* good things ...
Antonio
--
---------------
Antonio Carlini arca...@iee.org
Vic Gott
I have a copy of the XEBEC manual and am currently using one to run a
Seagate MFM drive on my own CP/M box. Unfortunately I am not in a
position to be able to scan the manual but will provide info if you
tell me what you need (I am in the UK by the way)
Vic Gott
vi...@nospam.farmore.net