Re: A couple of PET drive problems...

From: Bryan Pope (
Date: 2007-03-21 00:50:08

And thusly were the wise words spake by
> > Is there a webpage that describes how to measure the I/O signals?
> Have a look at the NRFD (Not Ready For Data) signal first. This signal 
> tells the computer that the drive is not able to receive data at all at 
> this moment. So have a look at this signal first: (L) means active and 
> the computer will wait until it is (H). So if it is (L) indeed, check 
> the level all the way up to the I/O ICs in both the drive and computer.


	A logic probe is also in my order from Jameco.  Once I get that 
(next week) I will check what you said.

> I read you replaced a 6522. In the drive or the computer? I had a 
> similar case and here the troubleshooter was the 6522 in the computer. 

	It was in the drive, from another working one.  I was going 
by the 2031 troubleshooting guide on which said if it
locks up while loading check the IEEE interface components and the 
ROM.  Another section (page-12l) titled "IEEE Interface" says all  
of the signals are controlled by device U3H (the 6522 I tried 
swapping) plus U1S (75160) and U1A (75161).  Hopefully I was 
going in the right direction!



       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail pre-2.1.8.