Picoscope 2204A
10Mhz bandwidth

 

I'm now by both boards installed,
Couple more discoveries, green led on good board is solid.
On bad board is flashing, seems to be driven via a 74hct04 inverter from a max 692 which is a processor supervisor?

The whole circuit is clocked by the special bus driver chip ams3609, clock signal is present at the processor xtal pin.

I need to read up on the max692

 

Picoscope 2204A
10Mhz bandwidth

Do you have two probes for the oscilloscope?
Do the probes have a x1 and x10 attenuation selection switch?

 

I'm now by both boards installed,
Couple more discoveries, green led on good board is solid.
On bad board is flashing, seems to be driven via a 74hct04 inverter from a max 692 which is a processor supervisor?

The whole circuit is clocked by the special bus driver chip ams3609, clock signal is present at the processor xtal pin.

I need to read up on the max692

Slow down!
I can't keep up with you.
If we have an oscilloscope we can check for some integrity of the 80C32 operation.

 

Yes 2 probes both with X1 X10 switch.

 

Here is the pinout for 80C32 and 8051.

 

Here is an example of what an 80C32 system board might look like:

 

So the first thing we want to look at is ALE on pin-30 of the 80C32.

 

Not a great picture 7 pulses at about 62khz

 

Have a look at the 74HCT573.



Set the switches to 75.
Trigger the oscilloscope with CHAN1 probe on /OE pin-1.
Look at LE pin-11 on CHAN2.

Next,
Trigger the oscilloscope with CHAN1 probe on /OE pin-1.
Look at one of the output pins, e.g. pin-12 on CHAN2.

We want to be able to see both channels simultaneously on your screen.

 

Both are at 5v solid no pulses,
Oe on that 74hct573 are driven by a multiplex number of which I'll have to go indoors to read!

 

74Hct139 drive's oe on the node address buffer

 

Which pin of the 74HCT139 is connected to pin-1 of 74HCT573?

We want to trigger the scope on /E while looking at A1 and A0, once we know which half of the IC is responsible for addressing the 74HCT573.

 

Thank you, there's going to be a brief (hopefully!) Break while I recover my pickup from the ditch my workman put it in (really)
I appreciate the time

Cheers Geoff

 

Thank you, there's going to be a brief (hopefully!) Break while I recover my pickup from the ditch my workman put it in (really)
I appreciate the time

Cheers Geoff

Sounds like fun!
I will be away for awhile too.

 

Don't seem able to upload picture!
Have a similar 62khz signal to ale on pin 13 of the multiplex.
OE is held high which I think stops the output.

The max 692 is effectively a watchdog, it sends a reset after 1.6 seconds, this reset pulse is also the green led flashing .

The good board has pin 7 connected to watchdog and is outputting a pulse.

The bad board isn't outputting the same pulse.

Ale is connected to le on the 74hct573 buffer on the eprom bus.

OE on the same buffer is connected to pin 6 on the 80c32 I have the board indoors now with no power supply but will try and scope the eprom bus and oe/pin6 in the morning.

I assume that buffer would be clocking the program into the micro?

A failure there would stop things wouldn't it!

Thanks Geoff

 

Pickup recovered, employee given a cuff round earhole

 

Still waiting to hear what drives /OE pin-1 of 74HCT573.
Is it a pin on the 74HCT139 or pin-6 of the 80C32?

 

Check which pins of the 80C32 connect to the output pins of the 74HCT573 (pins 12 to 19).

The 80C32 address/data bus is on pins 32 to 39. This a multiplexed bus that is shared between the 8-bit data and the low order 8-bit address.

 

Thanks I'll give it a prod with the multi meter.

There are quite a few 74hct573 on the board.

The one for the node address has its oe connected to pin 6 of the 74hct139, but as the watchdog isn't getting it's signal would I be safe to assume the program isn't running properly?

I don't think it's trying to get its node address as there isn't much happening on the input of the 74hct139.

There is a pair of 74hct573's to the processor's right , in between the processor and the eprom.

I've checked the first and it's outputs are to pins 32-39 of the 80c32.

Ale is connected to le
Pin 6 to oe

I don't have much time today but will try and get the board fitted and scope these pins later.

Thanks for your help and patience!