CFXII - Black screen with it plugged in

[Martin A]

The snippet of code reads data from the "silicon disc" data register, which auto increments so, as there's nothing resetting the sector pointers, the data should change each pass.

The important thing is it's not showning 120 which is what INP(xx) usually returns on accessing a non-existant I/O port. That and everything else is a good indication that the CPLD is behaving.

[acsi]

Did you check the power patch wire?

Yep the Serial Eprom is getting 3.3v and the patch wire to it from the resistor seems to be secure

[Martin A]

So a summary of what we've establushed:

• The MTX appears to be working fine apart from no sound output.

• With the CFX-2 installed the normal boot sequence hangs apparently waiting for the propeller to respond. The other boot options are working indicating that the flash with the Z80 code is fine. As is the section of the CPLD controlling the ROM paging

• The quick and dirty test of the silicon disc data register, appears to work and so the I/O side of the CPLD is probably good too.

• The serial EEPROM has been re-programmed/tested with no propblems and has a 3.3v power supply via the patch wire.

Corrupted data on the silicon disc could cause problems booting to CPM, but that wouldn't prevent the propeller starting up. That really does only leave the propeller or some of the passive componentss that surround it.

Aside from the chip itself, I can see a couple oof things that might stop a workimng propeller from starting up:

• The pull up resistors on the serial EEPROM clock/data lines are one possibility (10k R4 and R5 just above the EEPROM itself) as that could prevent the EEPROM code from loading.

• Another would be a short between pins 1 and 2 of J3 or "something else" holding the propeller in reset.

Obviously the propeller needs a 3.3v supply and a clock. However, the power is shared with the EEPROM and the clock with the Z80 and the main board so they're likely not an issue.

[acsi]

OK so the propellor chip arrived today and was promptly swapped in.

Black screen still. Although occasionally I will get this through the composite which is new behaviour



So the extra 32K is showing up OK.
Pressing Return I get the Ready prompt and can run the USER DIR command



And can load a program which proves the CF card still reads OK.



Sound is distorted and makes cracking sounds which probably proves the PSG is somewhat faulty.

The Serial Eprom errored when I tried verifying it again but seemed to blank and program OK although the programer seemed to get stuck for a bit around the area it errored on. I suspect the chip is faulty and do have some on order but they are not due until next week.

The pull up resistors on the serial EEPROM clock/data lines are one possibility (10k R4 and R5 just above the EEPROM itself) as that could prevent the EEPROM code from loading.

These measure 10K (9.9Kohm)

Another would be a short between pins 1 and 2 of J3 or "something else" holding the propeller in reset.

These pins do not show a short.

[Martin A]

That looks promissing. I would definitely suggest trying the build 281 ROM, see if that gets you a more consistent (or less!) start up.

Getting to the boot screen and running games is a good sign though for the z80 side of the board

What the new rom build does is force a software reset of the propeller every Z80 reset and not just on power up. The software re-boot can be done from basic with the exixting rom: From a sucessful boot to BASIC you could try the following short sequence of code

Code: Select all

5 VS 1: CLS
10 OUT 97,255
15 FOR X=1 to 40
20 PRINT X;INP(96)
25 NEXT

That should report 120 for the first 29 passes through the loop and then 0 from, 30 onwards after the propeller resets. The propeller output will show the test card. IF the test card appears then that would indicate an issue with the reset signal getting to the propeller, unlikely but worth testing. Poor contacts fron the bargain basement MTX edge connectors being a never ending issue.

iF that does work you could add

Code: Select all

30 OUT 96,27; OUT 96,155
35 FOR X=1 TO 10
40 PRINT X;INP(96)
45 NEXT
50 PRINT CHR$(27);"B0"

That will switch VDP shadow mode on manually. That is a faster opperation than the full re-boot and so the output there should flip from 1 to 120 around the 6th itteration. The last line will force a transfer of the character set to the emulated VDP without it the shadow screen just displays blue or white boxes.

If that works, then try

Code: Select all

USER VGA 1

[acsi]

That should report 120 for the first 29 passes through the loop and then 0 from, 30 onwards after the propeller resets. The propeller output will show the test card. IF the test card appears then that would indicate an issue with the reset signal getting to the propeller, unlikely but worth testing. Poor contacts fron the bargain basement MTX edge connectors being a never ending issue.

Gives me 120 right through to 40

I have put the new ROM version in and now cannot get the CFX boot screen but can still get the ready prompt with a Reset - M or Reset - Space and get the CPM Boot message with Reset - C

Hopefully the new serial ROM chip won't be far off.

[Martin A]

That's pretty conclusive, the propeller isn't even getting to the point where it starts monitoring the Z80 i/0 ports. Fingers crossed for the new EEPROM.

A quick test here with the VP-290 programmer, that talkes just over 21 sec to program and verify all 32k odf the 24LC256. I don't imagine any other programmers will be significantly different of a "good" write.

While I had the EEPROM pulled, I double checked the version. All the tests here were run wuth the Version 11 EEPROM (the May 2020 version) and either the 279 or 281 builds of the Boot rom.

[acsi]

Replacement serial eeprom arrived today. Quick program and verify with Monitor V11 and installed.

GRRRR... Black screen

Tried swapping the old propellor chip back in... Black screen

Tested Reset - C "CPM Boot" displayed on composite as expected.

Reset - M or Space gets me the Ready Prompt on composite as before.

Verified contents of EEPROMs are V11 and V281... check.

Checked 3.3v supply OK

Cleaned contacts on both sides again... Black Screen

short of a broken or dry solder joint I'm now at a loss

[Dave]

So, at this point, the only thing that is not working is the VGA output?

If so, can you check the short VGA adapter cable that the internal CFX-II uses

See this drawing http://www.primrosebank.net/computers/ ... %200.7.pdf

It’s probably worth double checking that the white plug is inserted properly too.

Regards
Dave

[Martin A]

Quick and dirty ROM hack enclosed.

It will still report 2.81 as I've just dived in with a hex editor and zeroed the 6 bytes that call the propeller initialisation routines within the normal boot sequence.

The test setup here will boot with the hack to the CFX startup screen and tones with the propeller disabled (by pulling the eeprom). That should give you all the SDX extensions and access to the CF while using composite/TV output for testing. NB A working propeller boots to the testcard and waits for 80 column mode data CMP mode would boot as normal.

I can only think of 3 things that would stop the propeller booting.
Reset remaining low
No clock input from the MTX
No communication with the boot eeprom

Obviously all 3 of those would happen if the propeller was plugged in backwards, and #3 if the eeprom was backwards. leaving the obvious aside:

For reset being released, check for a high on pin 11, I'm reading 3.7v or so at the pin with the meter here.
The clock input pin 30 is reading 1.8v on the meter which is about right for a 50:50 square wave from the 74S04 that drives Phi.
the crystal output on pin 31 that isn't used comes up as 0.4v
Checking the access to the rom on boot would need a scope.