ICE T80 is the version of the ICE that supports the Z80 processors.
GODIL Jumper Configuration
For the Z80, the GODIL jumpers should be configured as follows:
The black jumper connects the GODIL's GND input to DIL pin 29.
The red jumper connects the GODIL's VCC input to DIL pin 11.
The pins in the top left corner connect to the serial-USB cable.
- A1 is GND
- C1 is Serial Tx (GODIL -> PC)
- A2 is Serial Rx (PC -> GODIL)
These signals are 5V TTL Levels.
ICE-T80 Xilinx Design
The top level Xilinx project for this design is here: https://github.com/hoglet67/AtomBusMon/blob/master/Z80CpuMon.xise
The top level VHDL module for this design is here: https://github.com/hoglet67/AtomBusMon/blob/master/src/Z80CpuMon.vhd
Testing
ICE-T80 has been tested in the following systems:
- Spectrum +2B (successful)
- Spectrum 48K (unsucessful)
Spectrum +2B
Some photos of ICE-T80 in use on Spectrum +2B.
Spectrum 48K
Issue 4S board
There were issues caused by the split data bus (via R1 to R8, 470 ohm), in conjunction with the GODIL 1K5 pullups. This means that when the ULA or lower 16K of RAM was driving a 0x00, the GODIL was reading it as a 0xFF.
A scope showed that the "zero" voltage was actually 1.3V, which was being read as a "one".
Reducing R1 to R8 to 220 ohms reduced this to 0.7V, which was then correctly read as a "zero".
At this point the Spectrum would boot, and pass the memory tests, but the keyboard was not working. I suspect this is due to the voltage drop across D1-D8 in conjunction with the GODIL pullups. It's possible increasing the Xilinx drive from 4mA to 8mA or 16mA would help here.
For a schematic see here: http://www.retroisle.com/sinclair/zxspectrum/Technical/Hardware/ZXSpectrumIssue4ab-Schematics.gif
This was also discussed on the Forum, starting here: http://www.stardot.org.uk/forums/viewtopic.php?f=44&t=9655&start=240#p145560
At this point I gave up!