Modules with Z84C15 and KIO (Z84C90) on eBay

[Bill Shen]

I was searching for Z84C90 on eBay and run across this rather interesting and current equipment with Z84C15 and Z84C90.  This is eBay item 263771813956 used equipment for Matrix Platemate.  It looks like an embedded module containing Z84C15, RAM, EPROM, and KIO plugs into an application specific base board, so the same embedded module can be used for variety of different equipment.

The price is reasonable ($35+$19 shipping) but I already have couple working designs with Z84C15 as well as KIO so I'm not going to buy it.  If you are thinking about using Z84C15 & KIO, you may want to get this as evaluation platforms
  Bill

[Karl Albert Brokstad]

lots of nice stuff on these boards;

Karl

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Karl Albert Brokstad
Kirkeveien 9B, 5072 Bergen
98843314, 55289014
ka...@brokstad.no

[Bill Shen]

Seller lowered the price and I can't resist (this is why I have a big garage full of junks!) and bought it.  It is as I've expected that the Z84C15/ROM/RAM/KIO is a separate module pluged into a motherboard.  Here are the motherboard and the Z84C15 module.  I should be able to reuse the Z84C15 module, look like it is running at 19.66/2=9.83MHz.
  Bill

[Bill Shen]

While waiting for pc boards to arrive from China,  I've been puttered around with a commercial Z84C15 with KIO daughterboard that was a part of Maxtrix Platemate motherboard.  The pc boards from China will be here in a couple days, so I'm documenting the tearing down & modification of the daughter board (designated as OPALJENA) before I get sidetracked.

OPALJENA is a 3.3" X 4" 4-layer pc board consists of a Z84C1510, Z84C9010 (KIO), 32x8 RAM, and a ROM.  The oscillator is 19.66MHz which is divided by two to run the CPU at 9.83MHz. There are a couple glue logic, 74HCT139, 74F32 and a programmable logic.  The ROM is socketed so it is easy to replace it with my own software.

The first step is to find suitable VCC and ground, power it up and see what happen.  OK, no blue smoke, drawing a nominal current of 80mA.  There are activities on address lines, so that's all good.

Next step is locating the transmit and receive signals of Z84C15 and connect a USB-serial adapter to it, replacing the ROM with W27C512 with my own simple diagnostic and see if it will talk.  Attached picture shows the points of interests for the first couple steps.

The serial port does work, but it is running at 38.4K baud.  So while the processor clock is 9.83MHz, the I/O clock is 1/16 of that.  This is because the clock is divided by 16 with 74HCT139 and feed to both KIO and serial ports of Z84C15.

So far everything were done without modifications, other than replacing the ROM.  Further poking around show Z84C15's CS0 is wired to ROM gated by 74F32 with nMREQ; Z84C15's CS1 is wired to RAM also gated by 74F32 with nMREQ.  This is a problem because I won't be able to page out the ROM completely even though the memory map of CS0 and CS1 are programmable.  The critical area from 0x0-0x100 will always be ROM space.

So to make it capable of running CP/M, I need to make significant modification to the pc board. 

To be continued...

[Bill Shen]

The next step is replacing the 28-pin 32Kx8 RAM with 32-pin RAM (at least a 128Kx8).  The easiest approach is to disable the chip select of the 32Kx8 RAM and piggy-back a 32-pin RAM on top of it and move chip select to the 32-pin RAM.  With a little bit more work, I can cut out the 32Kx8 RAM and replace with sockets for the 32-pin RAM.  I chose the later because it gives me more flexibility with the choice of RAM.

Picture of board with 32Kx8 RAM removed and individual sockets inserted. 

Picture of board with 128Kx8 RAM

Make sure pin 2 is not floating and power it up.  OK, it is sending the same diagnostic message as with the 32Kx8 RAM, so the operation is successful, whew!

Now I need to spend time poking around and document the original schematic.  I'll need to do several cuts and jumpers to make ROM page-able and to create banked 128Kx8 RAM.
  Bill

[Mark T]

I think i would check the connections to the header pins above the rom and the unpopulated holes just to the left of rom and ram. There is a possibility the board was already configured to support larger memory devices.

Mark

[Bill Shen]

I plan to use the 28-pin W27C512 EPROM so I'm not too concerned about the 4 spare ROM sockets.  I did trace out 4 spare pins of RAM (pin 1,2,31,32); they are not quite what I've expected so I suspect I still don't fully understand their circuits.  My goal is switching out the ROM and running a monitor in RAM so I can poke around.  The programmable logic worries me, so I'm pulling out the KIO to minimize possible interaction.

  Bill

[Bill Shen]

I received the first batch of pc boards from China, so I'll wrap up what I have on OpalJena.  The board modification is complete, but not quite right.  I'm developing a monitor for it and got as far as copying program from ROM to RAM, but then something crashed.  Oh well, until next time.
  Bill