How can i test this board
almajiro opened this issue · comments
I finished solder this board. so i want to test it.
I burned the firmware to eeprom using tools from P8X Game System download page.
but, the board is doesn't work.
/WAIT signal is going to low immediately.
Then i burned the VT100 Emulator firmware and it works.
What are the possible causes?
Thank you.
Try to load the TMS9918 emulation firmware and run the ASCII.ASM code, this is the only example that doesn't require the WAIT line support.
thank you for your reply.
I burned the TMS firmware then I assembled ascii.asm using tasm on dosbox.
and tested with J.B. Langston's z80ctrl board.
but It didn't work.
I'm using 24LC256 instead of 24LC512. Can this be the cause?
I don't know how z80ctrl board works and if it has conflicts with this board, try to use the minimum required standard boards to test these issue, otherwise we can't know where the problem is.
The TMS9918 demo programs are meant to run from the standard monitor at address 5000h, so set the rom to load the standard monitor, upload the hex file produced by the compiler and run with G5000. Remove the WAIT line wire if this causes problems, for the ASCII demo it is not required.
The 24LC256 should work without problems, the current firmware is below the 32k limit.
I tested it with the SCM monitor program, but it didn't work. (i changed the .org to 8000 from 5000)
Does the TMS mode firmware output a VGA signal after the power is turned on?
Yes, all firmwares outputs the VGA signal.
Have you checked the board for shorts and bad solders ?
I checked the all connection via multimeter.
I have verified the firmware, both the release and the latest source, and both works as expected with the demo code.
If the VT100 emulator firmware works, at least the VGA connections looks working (both boards are using the same pins for VGA output, because of that you should always get a VGA signal from all firmwares), however the similarity stops here. Another difference is that this firmware doesn't display a blinking cursor only a blank screen (monitors should tell you if there is an active signal).
If the wait line is always asserted (and removing the jumper wire allows the Z80 to boot) makes me think that something is wrong with the VGA initialization but I can't think of a reason for that. I have used a stand-alone programmer (TL866) to write the firmware to the eeprom.
Other things to check are the diodes orientation (the black band should be on the upper side, near the Propeller chip), the transistor TR1 should be the correct type and with the correct pin disposition. I can't think of anything else.