Digital Discovery - can it handle 5V inputs? and how is the parallel data decoding?

[Matt Ownby]

I work with old arcade PCBs from the early 80's.

I have an arcade PCB with a hard-to-find defect and I'd like to use a logic analyzer on the 5V motorola 6809E CPU to trace the program execution and see where it's going wrong.

Ideally, I'd like to hook up the logic analyzer to all of the address lines (16), all of the data lines (8), as well as the read/write line, and interrupt lines to get a very nice picture of the program flow.  The cpu runs at 1 mhz.

So... since this is a 5V cpu, is this a problem?

And can the digital discovery's software independently decode the 16-bit address value and 8-bit data value (which will be valid on different phases of the cpu clock) ?

[Alex]

I think so.  It can decode 16 nit addresses and 8-bit data simultaneously 

• User programmable input and output LVCMOS voltage levels from 1.2V to 3.3V 3) (5V compatible 4) )

You can check details at https://reference.digilentinc.com/reference/instrumentation/digital-discovery/start

[attila]

Hi @Matt Ownby

Both the IO and input lines of Digital Discovery are 5V compatible, with VIO of 3.3V having logic threshold about 1.5V.
https://reference.digilentinc.com/reference/instrumentation/digital-discovery/reference-manual#io_level_translators
https://reference.digilentinc.com/reference/instrumentation/digital-discovery/reference-manual#input_dividers

Make sure to have ground connection between the DD and your circuit.

In the WaveForms application Logic Analyzer interface lets you capture up to 32 digital lines at a time:

 

[Matt Ownby]

35 minutes ago, Alex said:

I think so.  It can decode 16 nit addresses and 8-bit data simultaneously 

• User programmable input and output LVCMOS voltage levels from 1.2V to 3.3V 3) (5V compatible 4) )

You can check details at https://reference.digilentinc.com/reference/instrumentation/digital-discovery/start

thanks for the reply.

So the waveforms software has built-in support to decode cpu address and data lines independently of each other?

[attila]

Hi @Matt Ownby

In the Logic Analyzer you can use Bus interpreters with Enable and Clock signal for address/data decoding, and additional lines to visualize further control signals.