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Zeta SBC - Minimal, self-contained, N8VEM compatible Z80 SBC

sergey

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Zeta SBC is an easy to build Z80 computer, that I've designed this summer. It was pretty popular on N8VEM list and I sold out all the PCBs. Now I am considering to reorder PCBs. Perhaps people on this forum will be interested to build this system? (If yes - reply to this post :))

Here are the specifications:
- Small form factor (170 mm x 100 mm, 6.7" x 4"), can be mounted under a 3.5 floppy drive.
- CPU: Z80 (tested with NMOS and CMOS versions, up to 20 MHz, 6 MHz is required to support 1.44MB floppies)
- Memory: 512 KiB SRAM (system + RAM disk), 512 KiB flash (BIOS, CP/M, ROM disk)
- 8255 PPI. Can be used to connect an IDE hard drive or CF card using PPIDE, or for generic I/O
- 16550 UART - Console serial port
- FDC9266 floppy disk controller, supports common (that is IBM) diskette formats.
- RTC
- Runs CP/M 2.2, ROM images are available from N8VEM Wiki

More documentation is here: http://n8vem-sbc.pbworks.com/w/page/44366173/Zeta SBC

Update:
Tentative prices: PCB - $20, FDC9266 - $5, Shipping (one PCB and FDC - USPS First Class mail, no tracking) is $2 in US and $5 anywhere else.

Thanks,
Sergey

IMG_4667.jpg

IMG_4668.jpg
 
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barythrin

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Pretty neat little rig! Do you know roughly the cost of the components? I see the part listing but was curious if you already knew a ballpark figure.
 

sergey

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Silicon Forest, Oregon, USA
Pretty neat little rig! Do you know roughly the cost of the components? I see the part listing but was curious if you already knew a ballpark figure.

I did some calculations, and it looks like all the components for the entire system will cost about $100 (including shipping).
If you buy all components (except PCB, FDC and PPI) at Mouser, get PCB and FDC from me, and find 8255 PPI somewhere else for $5, it will cost $88.76 without shipping.
If you buy some components at Unicorn Electronics (logic ICs, UART, connectors, and capacitors are cheaper there, they have PPI too), and the rest from Mouser, it will cost about $75 without shipping.
 
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commodorejohn

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Couple of questions:

Is there a PLCC-to-DIP converter I can use for the Z80? I've got a 10MHz part laying around that's just begging to be put to use... ;)

I assume standard PC floppy drives will work? With a standard twist-cable, can I use two?
 

sergey

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Couple of questions:

Is there a PLCC-to-DIP converter I can use for the Z80? I've got a 10MHz part laying around that's just begging to be put to use... ;)

I assume standard PC floppy drives will work? With a standard twist-cable, can I use two?

You can build PLCC-to-DIP converter yourself using 40 pin DIP and 44 pin PLCC socket, some wires, and a hot glue to hold everything together (I built a 32 pin one when I was younger and had to reprogram a laptop BIOS). But I don't think it worth the trouble... 10 MHz Z84C00 in DIP package costs about $4. It looks like DigiKey has some adapters, but I bet they will be more expensive than $4 :)

Standard PC floppy drives work with a twisted cable. For a single floppy you don't have to use twisted cable, just use the second device (it should be possible to recompile BIOS so it will be the only device, if you like).

Update:
Found one at eBay: http://www.ebay.com/itm/NEW-Univers...Socket-Adapter-Converter-Module-/260898823796
Make sure to verify that it has the proper pinout.
 
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NobodyIsHere

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Dec 21, 2006
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Zeta SBC is an easy to build Z80 computer, that I've designed this summer. It was pretty popular on N8VEM list and I sold out all the PCBs. Now I am considering to reorder PCBs. Perhaps people on this forum will be interested to build this system? (If yes - reply to this post :))

Great Job Sergey! This is a wonderful SBC that is well designed and appealing. Very impressive work!

Thanks and have a nice day!

Andrew Lynch
 

MikeS

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Toronto ON Canada
Most excellent documentation!

Is the software also documented somewhere?

Can it be downloaded without jumping through the Subversion hoops?

Is CP/M ready to go, i.e. stick it into the ROM, connect a console terminal and press RESET?

What, if anything, is the diskette format compatible with?
 

sergey

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Silicon Forest, Oregon, USA
Most excellent documentation!

Is the software also documented somewhere?

Can it be downloaded without jumping through the Subversion hoops?

Is CP/M ready to go, i.e. stick it into the ROM, connect a console terminal and press RESET?

What, if anything, is the diskette format compatible with?

The software (BIOS) is mostly written by Wayne Warthen. I don't think there is much of documentation (other than source code comments). But Wayne usually is pretty responsive, so you can try asking him on the N8VEM list.

The stable firmware image, including BIOS, CP/M, and also source code and compilation tools and scripts (in case you want to modify something) is available for download from N8VEM Wiki.
The firmware also includes a monitor derived (and shared with) N8VEM project that can do all the basic stuff monitors do - analyze and change memory content, do I/O operations, etc.
Also there is a subversion repository, that is something new, and mostly used for developing new features.

If the power-on reset circuit works (which it usually does) you don't even need to press the RESET :) Just connect the terminal and plug in the power cable.

Diskettes are formatted using IBM PC compatible format (9 sectors/80 tracks for 720 KB and 18 sectors/80 tracks for 1.44 MB) and can be read / written on PC using programs like RAWRITE.
 

sergey

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An update and a question:
- I re-ordered PCBs, I should have them in 15 days or so.
- I will be ordering FDC9266 floppy disk controllers. Together with them I can order following ICs used in Zeta SBC (price is approximate, I will have exact one once I submit the quote):
Z84C0020PEC (20 MHz CMOS version of Z80 CPU) - $5
TMP82C55AP-10 (10 MHz CMOS version of 8255) - $4
SST39SF040-70 flash chips - $4 (I will program them with the latest firmware)
Anyone wants to get any of these ICs?
 

Tor

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Mar 14, 2011
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Norway/Japan
I would like (in addition to the PCB) also one of those FDC chips, and the Z80. (I would actually like to get all of those you list, but I have to be a bit careful because if the total value w/o shipping goes above (at current exchange rates) approximately $33 I suddenly get to pay nearly $40 extra, in VAT and customs handling charges.)

-Tor
 
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