hey whats the proms clock speed for the 165?? or how fast is the thing running...thanks

 

You should use a minimum of a 250 nsec access time EPROM. The clock speed is 8.388 MHz, which is then divided by 4, of which part of that time is spent putting the address onto the bus. Could get away with a 350 nsec access time but I wouldn't want to.

The reason is that you need a good margin of error for the temperature and voltage extremes an automotive device endures.

Hmm, guess that was the long answer. . .

RBob.

 

i know for sure it takes a clock pulse to transfer data to the latches and then one to to shift it, but i wonder why its divided by 4...hmm so it could be in the 1-2mhz region huh ...thanks

 

Not sure what you mean but the bus speed is the 8.3xx clock divided by 4: 2.079 MHz. The Motorola bus has separate data and address lines. This gives a 477 nsec cycle time.

The address is presented, then at the end of the cycle the data is read. 477 nsec later. Give or take 100 nsec to apply the address and the access time is at a maximum of 377 nsec.

The hold time is built into the bus as the propagation delay is in the CPU to change to the next address.

I use 250 nsec EPROMs on a regular basis (on the '730, a P4 ECM at the same speed) with no problems. I've had a scope on the bus many a time. . .

RBob.

 

thanks for the info ........the reason i asked is that i built a thingy lets say for it and im looking at maybe some board inductance that is messing with the outputs and was needing to know the bus speed thanks alot.. you da man!