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by Bill B
11 Jan 2021 10:10
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

Spoke too soon :(

I have fixed low speed mode, but broken high speed, it is triggering too soon. I will have to see what, if anything, I can do about that.
by Bill B
10 Jan 2021 16:42
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

Screenshot from 2021-01-10 14-19-30.png
Screenshot from 2021-01-10 14-19-30.png (68.11 KiB) Viewed 133 times
Progress :D

Having modified the VHD to only test for I/O to port 0x49 on the rising edge of PHI, the spurious fast pulses have gone away, and the SD card is responding to the Z180.

I now need to write lots of code to make use of it.
by Bill B
10 Jan 2021 14:00
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

My cheap logic analyser has arrived and is proving illuminating: Screenshot from 2021-01-10 11-13-48.png It appears to show that I am frequently, but not always, getting a spurious ninth pulse at the end of a low speed SPI byte. Zooming in shows that the "ninth pulse" is not a single pulse, but a bu...
by Bill B
03 Jan 2021 17:19
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

No, Propeller chip is not fast enough :(

I might have been able to do something with my Teensy 3.5, but instead have ordered the cheaper version of Martin's suggestion.
by Bill B
02 Jan 2021 23:27
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

No, don't have any form of logic analyser. Only an ancient two channel scope full of lots of glowing tubes. I have in the past used PiScope and connected RPi GPIO via voltage dividers. However that has a maximum sample rate of 1MHz, which is not fast enough for this application. Also see previous po...
by Bill B
02 Jan 2021 17:50
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

20201229_160008.jpg Progress is proving painfully slow :( Testing the CPLD using an RPi to bit-bash inputs and monitor outputs (illustrated) led to the discovery of one logic error and one typo in the VHD for the CPLD. Corrected the VHD, reprogrammed the CPLD and tested again. Looked OK. Tested wit...
by Bill B
22 Dec 2020 09:59
Forum: OFF TOPIC
Topic: Coprocessors for BBC micro
Replies: 2
Views: 155

Re: Coprocessors for BBC micro

Yes, the Pi Zero can be hard to find (although I notice that PiHut have them in stock at the moment). The ZeroW (or WH) is often easier to find. And that would offer the possibility of adding WiFi to the MTX. Although the PiTubeDirect is bare metal, and I don't know whether anyone has got WiFi worki...
by Bill B
21 Dec 2020 18:09
Forum: OFF TOPIC
Topic: Coprocessors for BBC micro
Replies: 2
Views: 155

Coprocessors for BBC micro

Very off-topic for this forum, but I know Martin at least is a BBC micro fan.

I came across an article in the MagPi magazine of using an RPi to emulate multiple second processors for a BBC micro. Details can be found here.
by Bill B
21 Dec 2020 17:56
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 89
Views: 25578

Re: Another Home-Brew - Z180

So, ever optimistic, I wrote some Z180 code to test reading and writing an SD card. Of course it does not work, fails on the first step of initialising the card :roll: So back to trying baby steps. Remove the SD card adaptor, and link the MISO input to the MOSI output. This should resulting in recei...
by Bill B
19 Dec 2020 17:30
Forum: REMEMOrizer
Topic: Case/Extension Cable?
Replies: 26
Views: 6826

Re: Case/Extension Cable?

Pi in an MTX case? Dave's already done that: http://primrosebank.net/computers/mtx/p ... inside.htm