Z80 debugging with DSLogicPlus Logic Analyser

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DSLogicPlus Hardware

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Project Description

This web page is a collection of notes I used when I setup my DSLogic plus logic analyser. The DSLogic plus is a small hardware USB device used to sample up to 16 logic lines and display the results on the PC screen in various formats. The software component is called DSView. My first use of this device was to debug an interrupt driven serial routine on a S100 Z80 processor board.

DSView software

DSView Software(click to enlarge)

The logic analyser hardware uses an FPGA to monitor the logic lines and record and timestamp any transitions that occur. It also has programmable trigger logic that can be used to start data collection on user specified events. The data collected by the hardware dongle is passed to the PC using a USB connection and is displayed on the PC screen by the program called DSView.

Key Features of the DSLogicPlus

System Requirements

When using a logic analyser, there are many ways to connect to your circuit under test. With 16 signals and 16 ground connections, I didnt really want to use the gripper clips that came with the DSLogicPlus. I decided to use pin headers that I hot glued to the back of my test board and wired the pins into the key z80 signals right on the Z80 socket. This allows me to plug the analyser on quickly with the board installed in the system bus. The next photo below, shows the DSLogicPlus connected to my cpu board and the picture below it shows the connections from the pin headers to the Z80 chip. The blue wire on the right runs off to a spare output port strobe (out 0dfh in my case). By inserting an out instruction in my code, I can set up to trigger on that point and see what the code was doing around that area in the program. dsv-connections.jpg

S100 Bus with DSLogicPlus Connected

Pin Header connections to PCB

Two rows of 16 pins were used. The row closest to the PCB is all ground pins and the 16 upper pins are all the signal pins.

DSView Setup Instructions

Rather than fill this page with details of software setup, I have put all the instructions in a text file dsv-for-z80.txt(6K) that you can print out to follow along when setting up the software. Your situation will probably be different, but the notes will help setting up DSView. The setup is not complicated if you can visualize what you want to watch for. You need to hook the analyser lines up to the hardware under test, tell DSView what each signal line is called, decide how fast and long you want to sample and what you want to trigger on to start the sampling. If you are using one of the built in decoders, you need to configure the decoder to match the signals on the wires.

Electrical Drawing(s)

Z80 CPU Pinout - dsv-z80.png(120kB)
Z80 Serial Dart Pinout - dsv-dart.png(129K)

Source Code

DSView Config File - dsv-z80-dartb.dsc(11K)
DSView Setup Instructions - dsv-for-z80.txt(6K)
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