MC6802 Motorola how to test advice needed

[simoV8]

G'day all
Can anyone tell me the best way to test an MC6802

Thanks

Simon

 

[Nigel Goodwin]

G'day all
Can anyone tell me the best way to test an MC6802

Build a circuit, write a program for it, and see if it works!.

There's not much else you can do - there's nothing much you can test without a running program.

 

[simoV8]

The 6802 is in a pinball machine , and i was looking for pinout voltages, or logic probe readings, or the best way to check it,,????

thanks
Simon

 

[Nigel Goodwin]

The 6802 is in a pinball machine , and i was looking for pinout voltages, or logic probe readings, or the best way to check it,,????

From what I remember, the 6802 is an old micro-processor, as such it requires an external clock, external RAM and ROM, and external interface components. What you can check is highly dependent on all those.

For a start I would use a scope to make sure you have a clock input, and to check for high speed data on the data and address busses. I would also check that the reset circuitry is working correctly.

Micro-processors are usually very reliable, particularly an old one like this (where anything nasty is connected via an external chip), it's not very likely to be faulty.

There are only two real ways of testing it - either try a known working one in it's place, or try this one in a known working application.

 

[simoV8]

Thanks Nigel .

I'll get another mc for it and try it.
Why is there no read write readings ???
there's 4.9 volts at the correct spots (Apparently)

Thanks and apreciated

Simo

 

[Nigel Goodwin]

Thanks Nigel .

I'll get another mc for it and try it.
Why is there no read write readings ???
there's 4.9 volts at the correct spots (Apparently)

The problem with any micro design is you don't get many static voltages, the +ve supply to the chip and the reset pin are about the only ones. Every thing else is likely to be switching high and low at varying speeds.

 

[simoV8]

I used a logic probe ( the First time i've used one ) Set to TTL, every pin exept for pin 34? R/W had a reading, is that normal ???

 

[Nigel Goodwin]

I used a logic probe ( the First time i've used one ) Set to TTL, every pin exept for pin 34? R/W had a reading, is that normal ???

I've no idea, I've never used one - but there's not a lot you could check with a logic probe on a micro-processor.

 

[simoV8]

Is the scope the only way to go then , could you give me advise on scope software ??.

Thanks for your all your advise Nigel

Simo

 

[Nigel Goodwin]

Is the scope the only way to go then , could you give me advise on scope software ??.

A scope doesn't help a great deal either, basically it can only show high, low, or varying data - not what the actual data is. A logic analyser is often used to help you see what's going on.

As regards scopes, you are far better with a proper scope, rather than a PC software one - although a PC software one will usually work as a fairly low spec storage scope, which might be useful.

Micro-processor systems are generally hard to fault find, what is the problem with this one?.

The most common faults are generally with sensors and external interfaces, micro-processors them selves are usually very reliable.

 

[simoV8]

I've got schematics for the MPU , any chance of you having a look at them ??

Thanks again

Simo

 

[Nigel Goodwin]

I've got schematics for the MPU , any chance of you having a look at them ??

Stick them on a web server and post the URL and I'll have a look, but what's wrong with it anyway?.

 

[simoV8]

I've got schematics for the MPU , any chance of you having a look at them ??

Stick them on a web server and post the URL and I'll have a look, but what's wrong with it anyway?.

The MPU Led stays On.
It should flash a few times to signal start up shoudnt it ????

 

[simoV8]

Nigel,
I"ve had a sqizz, (look ) at ya ,(your) sites, . and realized I might be barking up the wrong tree, i'm new to this kind of electronics and have lots more learning to doo

Thanks for ya help so far (thanks for your replies)

WARNING, i'll be back with more questions.

SimoV8.

 

[Nigel Goodwin]

The MPU Led stays On.
It should flash a few times to signal start up shoudnt it ????

I've no idea, it depends entirely on how it's connected and what it's designed to do - it might just be a power on LED?.

 

[simoV8]

Thanks again Nigel,

I"m gonna (going) to work out how to read the shitty schematics i've got for it , (there real smudgy), i'll see how i go.

Simo