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Old eprom programmer help.
- Thread starter samib71
- Start date
daver2
10k Member
I am out at the moment so I will have a look tomorrow.
There are a couple of very strange readings there though (U7 pin 5 and U12 pin 4 for instance).
Dave
There are a couple of very strange readings there though (U7 pin 5 and U12 pin 4 for instance).
Dave
daver2
10k Member
I would normally say no to that to start with...
I have just finished for the day. So I will have my tea, do the washing up and them have a look at your traces.
Dave
I have just finished for the day. So I will have my tea, do the washing up and them have a look at your traces.
Dave
daver2
10k Member
Tea in the UK can mean a cup of tea, or a meal in the early evening. This was the latter.
Some of your Z80 signals do not look that good. They are not sharp-edged and don't seem to fully go either to 0V or VCC. This may be how you have configured your oscilloscope ground reference or where you have connected your oscilloscope 0V clip to.
U12 pin 4 is wierd at 2V?
The important thing is no /IORQ signal...
Can you find C5 (a 47 uF capacitor) with one side wired to 0V and the other side wired to the Z80 pin 26 (/RESET pin)?
If so, can you solder a normally open pushbutton across the two pins of C5? This will act as a manual reset button.
Can you use your oscilloscope to monitor the /IORQ pin of the Z80 and then press and release the manual reset button you have just soldered in.
Let's see if we get any /IORQ pulses at all when we hit a reset before something goes into the weeds...
You may need to slow down your oscilloscope timebase a bit (or select single trigger mode so that the oscilloscope triggers on a HIGH to LOW edge of /IORQ so that we capture the event without losing it with further triggering)... If you don't see anything, you can always practice on /MREQ first...
Dave
Some of your Z80 signals do not look that good. They are not sharp-edged and don't seem to fully go either to 0V or VCC. This may be how you have configured your oscilloscope ground reference or where you have connected your oscilloscope 0V clip to.
U12 pin 4 is wierd at 2V?
The important thing is no /IORQ signal...
Can you find C5 (a 47 uF capacitor) with one side wired to 0V and the other side wired to the Z80 pin 26 (/RESET pin)?
If so, can you solder a normally open pushbutton across the two pins of C5? This will act as a manual reset button.
Can you use your oscilloscope to monitor the /IORQ pin of the Z80 and then press and release the manual reset button you have just soldered in.
Let's see if we get any /IORQ pulses at all when we hit a reset before something goes into the weeds...
You may need to slow down your oscilloscope timebase a bit (or select single trigger mode so that the oscilloscope triggers on a HIGH to LOW edge of /IORQ so that we capture the event without losing it with further triggering)... If you don't see anything, you can always practice on /MREQ first...
Dave
daver2
10k Member
If this doesn't yield results, I can write you a small test program to burn into an EPROM for U8 that will write to the display ports and see what we happens...
Dave
Dave