hi everyone,

Have not got long...Im making a z80 computer for a uni interview which is tommorow. It was working until today....

Here are two problems..
My EEPROM has a power supply of 5V, I checked this. Why is it that when the Z80 enables the chip the data lines are about 3.5V

The Z80 also has a suply of 5v. Why is it that too the control pins are about 4v and not 5?

I send the halt instruction from the eeprom (01110110) and i know that it is in the memory but the z80 does not execute the halt. (i checked the data pins and wires etc....)

Thanks very much
Robin

 

How about schematics It could be that something is loading the CPU to much. Do you use buffers on the data and address bus

 

Just a guess here, but a lot of the logic of this era was related to TTL. TTL uses 3.4V for a logic 1, and less than 0.7V for a logic 0.

 

Do you measure with a scope or DMM? Remember the signals are very dynamic
on a CPU

 

sorry guys, fixed it XD
My bloody fault....forgot to connect A10 from the EEPROM, twas floating

All is good... Oh i dont have the schematics as they are on my other computer AND there are no buffers