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CMB PET 3032 ( 2001N BOARD )

Use channel 1 of your oscilloscope to monitor the /CAS0 pin of the 'I' bank of DRAM.

You should observe four (4) low pulses occurring between every two (2) pulses of UD8 pin 20 (channel 2 of your oscilloscope).

If this is correct, align your existing marks on your piece of paper with the UD8 pin 20 pulses and mark the /CAS0 pulses on the paper in a different colour pen.

Old schooling it here!

Dave
 
What you have now is UD8 pin 20 pulses indicating the start and end of a test.

The /CAS0 pulses indicate a unique access (write to or read from) the DRAM.

The first /CAS0 cycle is a write ($00), the second cycle is a read, the third cycle is another write ($FF) and the forth cycle another read.

Move your Y1 probe from the /CAS0 pin and put it onto the R/W pin of the DRAM.

Align your bit of paper with the UD8 pin 20 pulses.

Look at where the markings are for the /CAS0 signal on the paper.

The R/W signal should be LOW for cycles 1 and 3 (write) and HIGH for cycles 2 and 4 (read).

Dave
 
Hang on,

Have you changed the timebase?

I am expecting to see UD8 pin 20 (Y2) on the screen at the same time as the signal we are monitoring with Y1...

Dave
 
Post #1,089 is not making sense to me then.

Can we go back to those signals and separate the two traces vertically so we can see the two traces individually.

Dave
 
Desperado, when using x10 probes, the scope Attenuators for comparing two traces are both better set on 0.2V/div. That way each recording of TTL signals is only about 2 divisions (4 volts) high, then it is easier to separate the two traces vertically with some space on the screen. If they overlap because the amplitude is too high (as it is with the 0.1v/div setting you had on post #1089 and #1090), it gets hard to see what is going on.
 
But where have our 3 pulses gone from channel Y2 (as indicated in post #1,091) thatcwe are using as our oscilloscope trigger?

Dave
 
Desperado, when you take the photos of the scope recordings, can you angle the camera so that Daver2 can also see what setting the timebase knob on the scope is pointed to. These are cut off in your photos, providing less information.

Daver2 is trying to fix your computer by "remote control" and it will help him a lot if he has all the information. He is not psychic. If he cannot see some of it, then he has to use a Crystal Ball, which are known to be unreliable at the best of times.

Though some fortune tellers came up with very good answers to questions. For example in the movie "Pee Wee's Big adventure" Pee Wee went to a Fortune Teller to ask where his stolen bicycle was. He thought he would test the fortune teller out, so he asked; " if you are so good, tell me why I am here ?" The fortune teller replied; "You are here because you want something". At that point Pee Wee's eyes glazed over and he handed her his entire wallet.
 
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