Re: 2445 EPROMs

Chuck Harris <cfharris@...>

Back in those days I was always and Intel guy.

Customers forced me to learn Motorola 6800 and 68000, but
it wasn't a labor of love, so I have forgotten almost
everything I ever knew about them.

And my data books for them are ...somewhere...

Thanks Mark!

Mark Litwack wrote:

Hi Chuck and Chris,

The external clock input on the 6802 is divided internally by four to create an internal two-phase clock (one phase is output as signal "E"). So, with a 5MHz input, the cycle time is actually 800ns, which well within range of the Intel D27128 with 250ns access time I mentioned before.

There is also the NOP exerciser which can be enabled with jumper P503. This is good for getting to the bottom of possible processor and/or bus buffer issues by looking at E, address lines, and other signals as the processor is looping. Its operation is described in the service manual.

I do recall one instance of a bad processor, but granted, they are rare.


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