Correct resistor for a circuit?

[granddad]

Hi Tony... the OP problem has moved on is not about leds or resistors now its about how to get a Z80 to read 65,000 NOP's !

 

[Tony Stewart]

so does that mean LED duty cycle is as low as I thought or do MSB address lines toggle?

 

[granddad]

As far as I can see the 16 address bits are stuck .. possibly all at 1's ...

 

[halleffector]

As far as I can see the 16 address bits are stuck .. possibly all at 1's ...

Yes, this is exactly the problem.

All address lines are set to 1 after a few clock cycles have passed, and remain at 1 indefinitely. There is no counting so the CPU does not increase the program counter.

 

[granddad]

Still here ... I have the Z80 pensioner under PIC control, signals more or less as DS ... the Reset ( PIC generated) shows how first instruction fetch is achieved ,(M1 & Read ) the wait (PIC generated ) allows control over memory access. just in the process of designing a better control circuit... ( Bus Pirate is ace )
Z80 clock at +- 20khz

HE if your reset switch bounced during or after zero state , or not low for the 3 clocks , then Z80 = unknown state ?

 

[halleffector]

Still here ... I have the Z80 pensioner under PIC control, signals more or less as DS ... the Reset ( PIC generated) shows how first instruction fetch is achieved ,(M1 & Read ) the wait (PIC generated ) allows control over memory access. just in the process of designing a better control circuit... ( Bus Pirate is ace )
Z80 clock at +- 20khz

HE if your reset switch bounced during or after zero state , or not low for the 3 clocks , then Z80 = unknown state ?

View attachment 100071

What is zero state? The state the CPU enters when RESET is held low?

I think I should start a new thread for this problem, since it has moved away a lot from the original question the thread states.

 

[granddad]

HE , Agree , new thread. you did get over 1000 views here ... I expect not a great interest in Z80 now, re problem perhaps a faulty connection on the bread board ?