MC 6802 with no read write

[simoV8]

G'day guys ,

I'm still trying to figure out why there is no read write on the MC6802.
It's in a pinball mpu, (IC 1 ) , the circuit board tracks etc ,are in great
condition, it has an external crystal ,,,, could that be the problem ???

 

[TillEulenspiegel]

The 6802 is an 8-bit MPU with Bidirectional I/O lines that are toggled by an I/O assignment line. It has it's own internal clock so the outboard crystal isn't the problem...in fact You don't mention what the problem is.
It would help if you made clear the symptoms and any other pertinent info .

edit : sorry I wasn't clear .......The read write lines are the same . The function of either read or write is handled by the W/R line.

 

[simoV8]

why is the external (outboard)crystal there if it's not needed ??

 

[simoV8]

What i should have asked ,, why is the outboard crystal there ,
(if it's not a problem) ,,, i am new to this sort of eleltro .

thanks till

 

[Nigel Goodwin]

What i should have asked ,, why is the outboard crystal there ,
(if it's not a problem) ,,, i am new to this sort of eleltro .

thanks till

As far as I'm aware the 6802 uses an external clock, you could always check that it's oscillating with a scope - but use a x10 probe, or the scope will stop it oscillating anyway.

You should probably download the datasheet for the 6802, so you have an idea of what's needed.

 

[simoV8]

i'll test that, (i will get that tested)

Thanks