S-100 kit building

[lynchaj]

Hi,

I found an interesting website with a technical manual for the System 80 with schematics for Z80 to S-100 bus interface.

http://www.webweavers.co.nz/system-80/manuals_technical.htm

This may be very useful information in building a bus bridge board from my Z80 ECBbus system to an S-100 bus.

Thanks!

Andrew Lynch

PS, my IDE HD project is nearly complete hardware and the CBIOS is feature complete and in debugging presently. It seems to work but last nights testing revealed a pretty major bug which was easily fixed. If anyone wants to build one of these IDE HD interfaces and use it in CP/M, let me know. I can post hardware design info, parts lists, sample code listings, CBIOS, etc. The CBIOS needs some optimizing though.

[ahm]

If anyone wants to build one of these IDE HD interfaces and use it in CP/M, let me know.

I'm curious how your design compares to/improves upon Tillman Reh's GIDE (http://www.gaby.de/gide/) interface?

Thanks,
Andy

[lynchaj]

I'm curious how your design compares to/improves upon Tillman Reh's GIDE (http://www.gaby.de/gide/) interface?

Thanks,
Andy

Ahm,
I wrote a reply yesterday but apparently it never managed to post. Oh well.

In short, the difference between my circuit and GIDE is they use programmable GAL chips which can be hard to get and require special programming hardware ($100-$300) to make yourself. You buy them preprogrammed but that rather defeats the purpose of building from scratch. My circuit uses 8 standard and commonly available 74LSxxx chips and is easy to make and get the parts.

My circuit has all the design info available including parts list, schematics, test software, and a working CBIOS. That information is also available for GIDE but it is scattered about the internet.

I do not have any problem with GIDE as it is a fine interface but it uses GALs which are not homebuilder friendly in my opinion.

Thanks!

Andrew Lynch

[lynchaj]

More information on the S-100 expansion bus for the System 80. Apparently there were some S-100 expansion bus devices created for the platform. The most direct System 80 <-> S-100 interface is the X-4024 found here:

http://www.webweavers.co.nz/system-80/manuals_tm3_drawing%204.15_X-4024%20S-100%20interface%20schematic.jpg

This circuit is appealing but would require additional logic between it and the ECB to properly create the signals it is expecting to be present on the System 80 expansion connector. Those appear to be very similar to the TRS-80 Model I bus control logic.

Regarding the Z80 to S-100 bridge, the Exidy Sorcerer had an expansion chassis using very similar Z80 bus signals on their expansion connection. Full schematics for the computer and the S-100 chassis are available here:

http://www.trailingedge.com/exidy/

In addition, there is an excellent book I just bought which addresses the theory behind the S-100 bus and also other contemporary microcomputer buses such as TRS-80 I. Interestingly, this book has an appendix on the conversion of the TRS-80 I expansion bus to the S-100 bus including circuit diagrams. The TRS-80 I bus is Z80 based and similar in principle to the ECBbus which could be a very direct path for an ECB to S-100 bridge circuit.

http://www.amazon.com/gp/product/0672218100

Thanks!

Andrew Lynch

[chuckcmagee]

I built a S-100 to TRS-80 bus converter in 1981. Tandy had a voice synthesizer that I wanted to use. I got the bus converter diagram out of a Popular Electronic mag. I got the thing talking fine so it does work.

[lynchaj]

I built a S-100 to TRS-80 bus converter in 1981. Tandy had a voice synthesizer that I wanted to use. I got the bus converter diagram out of a Popular Electronic mag. I got the thing talking fine so it does work.

Would you mind scanning that article and posting it here?

Thanks!

Andrew Lynch

[chuckcmagee]

Well, I did this in 1981 -- the magazine is LONG gone, think I have moved 8 times since then.

[lynchaj]

Well, I did this in 1981 -- the magazine is LONG gone, think I have moved 8 times since then.

OK.

Maybe someone with the magazine will see this thread and post the article. I'll bet someone on these forums has that magazine sitting somewhere on a shelf.

Thanks!

Andrew Lynch

[lynchaj]

Hi!

Did some more research on this project and found a book based on a recommendation here called "The S-100 & Other Micro Buses" by Elmer Poe and James Goodwin. I believe this book holds the keys to unlocking the Z80 ECBbus to S-100 bridge project.

I have made a brief scan of some of the book to illustrate my point. I recognize the work is copyrighted so I claim this is "fair use" under the education exemption as this is engineering continuing education project. At any rate, the scan is quite brief and not the entire work so if anyone has any problem with it, I will remove it. Unfortunately, I cannot attach it to this message as it is too large (~1.8 MB).

The general outline of the project is in two major components:

First, is a Z80 ECBbus to TRS-80 Model I conversion board mounted on the ECBbus passive backplane. The ECBbus already contains most buffered Z80 bus signals for the address, data, and most of the control lines and they should provide sufficient information for this project. The basic schematic is a subset of the circuit on pages 44-51. The primary exceptions being /RAS (pin 1), /CAS (pin 3), and MUX (pin 16) will not be connected as they have no corresponding S-100 counterparts on the other side of the interface. This is actually a lucky break since /RAS, /CAS, and MUX are used for DRAM address decoding. They are timing sensitive and derived from the TRS-80 Model I 10.6445 MHz clock which is not present on the Test Prototype. Some signals will have to be added to my existing Test Prototype ECBbus subset such as phi, /M1, and /HALT. Fortunately, those signals are already part of the ECBbus standard so they should not cause an issue. The ECBbus bridge board would export its signal via 40 pin braided cable and IDC headers.

http://www.hardwarebook.info/ECBbus

Second, is an S-100 interface board with the circuit captured in the schematics on pages 167-170. It would be connected to the first board via a IDC header and the 40 pin braided cable. The S-100 card would be plug into a passive backplace S-100 motherboard and the bridge board would control the bus. I plan to make the S-100 card using a wirewrap prototype board. Eventually, it may get replaced with a custom PCB as S-100 cards are scarce and I would like to avoid permanently dedicating one.

So, that is the plan. Anyone have comments or questions?

Thanks!

Andrew Lynch

PS, I found an earlier version of the S100 book online at:

http://www.hartetechnologies.com/manuals/Unclassified/S-100_and_Other_Micro_Buses.PDF

The pages numbers are probably wrong but the content and relative locations are the same.

This project is in slow motion as I finish up the FDC for the Test Prototype and get my S-100 Chassis rebuilt. I ordered some S-100 prototype boards so it is still moving. The next step is to translate the diagrams into real schematics and layout a circuit.