VDP - No Output TC01

[MOTE]

On my TC01 I have perfect output from the 80-Column Card but no colour signals from the VDP outputs. This hasn't worked since I obtain the machine.

I checked VDP input signals /CSR and /CSW from IC32 pins 6 and 8 respectively, they are stuck Hi but /RD and /WR are changing state. The above two outputs of IC32 are controlled by signal /VDP from IC26 14 pin which is also stuck Hi. IC26 is obviously functioning as expected for other outputs as those associated features are working.

Before I dismember the computer to replace IC26 (LSl38) is there a 'switch' anywhere that could stop the colour graphics from being produced?

Mike

[MikeDHalliday]

Have you checked that the jumpers are set to RGB output and not the standard YUV?

https://re-enthused.com/information/tat ... art-cable/

Check the images here for the jumper settings

It might help?

Regards
Mike.

[MOTE]

Thanks Mike but that is way upstream from the problem, /VDP isn't even changing state to enable the processor.
I have changed IC26 as this is the source of /VDP but to no effect.

I discovered that link block M003 in the 80 Column module dictates, at switch on, if the video defers to the unit or standard. I hadn't thought to look in module manuals as I had already tried with the module disconnected. in the position the link was in I would never see VGA out. With the link swapped over the 80 column output did indeed stop but I had also read that CTRL-P should change from normal to 80 col video out but it doesn't have any effect other than to cause some boot disc activity! The manual doesn't mention if there is a CTRL sequence to change the other way; from the default of 80 to standard colour out.

The MOS ROM is version 1.21 so higher than than 1.1 as required for the 80 column module; what changes were made with those versions?

I have checked the address and /MREQ/M1 signals into IC26 using my Picoscope 2205MSO and all are present with some changes present when a continuous stream of characters are sent. I do not know if they are in the right order to produce output /VDP. I have to investigate if it is possible to set up a pattern match in the Picoscope but as they not creating the required output I presume something is out there and I am suspecting it lies in the firmware.

Mike

[MikeDHalliday]

Sounds like you have an uphill struggle there!

I seem to remember CTRL+N being the switch the other way.

I have it labelled on my Einstein, but its packed away so cannot check at the moment.

Do you get UHF output to an analogue TV (if you have one)?

[MOTE]

Nothing from the RF end of things, as I say the VDP is not being enabled.

Thanks for the hint about CTRL N; I will give that a try to see what happens.

Next steps:
1. What MOS ROM version does everyone else with a TC02 80 column have in use?

2. I am wondering if there is an error in the MOS ROM EPROM; is there a binary file available for 1.21?
If so I will pull the 2764 EPROM and compare them.

3. Is there a MOS ROM source listing available for any versions higher than 1.1?

Mike S

[MikeDHalliday]

I have MOS 1.2 in mine Einstein and it works well with my 80 col card.

Have you tried the diagnostic firmware?

I thought I might have had a ROM dump somewhere but I can't seem to find it, just the diag firmware.

http://tatungeinstein.hopto.org/8-bit/T ... ourcecode/

You might find what you are looking for at the above link, I have not indexed anything, just dumped what I have into a set of folders.

[MOTE]

Mike, sorry I didn't come straight back; I didn't know you replied as, despite notifications for everything being turned on and subscribed to the topic I am not getting any notifications and they are not going into spam. Oops! I just noticed the need for a tick in the box below.

Many thanks for the link, lots of good material there but I found the binaries for 1.2 and 1.2.1 elsewhere.

I must rig something up to easily transfer files to the Einstein, probably 3.5 floppy and sort out a Gotek if I get everything working. Any preferred suppliers for the Gotek?

Mike