Do I need drivers?

[digital_dave]

I have two boards connected by up to 209cm of ribbon cable. Both boards are 5V 'LS TTL logic. I am new to electronics (on gong web based self learning) and I don't have a great feel for the analog side of things just yet. I suspect (from reading snippets here and there) that the signals between the two boards may get affected by attenuation and noise. Is this a definate situiation? Will I need drivers or should I prototype the boards and see if problems occur?

thanks,

David

 

[Nigel Goodwin]

I have two boards connected by up to 209cm of ribbon cable. Both boards are 5V 'LS TTL logic. I am new to electronics (on gong web based self learning) and I don't have a great feel for the analog side of things just yet. I suspect (from reading snippets here and there) that the signals between the two boards may get affected by attenuation and noise. Is this a definate situiation? Will I need drivers or should I prototype the boards and see if problems occur?

How fast will the signals on the ribbon be running?, the capacitance of the cables will limit how fast the signals can change - when it goes high it has to charge the capacitance of the cable, and when it goes low it has to discharge it. As the switching speeds get higher, this starts to give problems because it limits the rise and fall times.

 

[digital_dave]

The boards are a old Z8000 based processor board and a led and keypad front panel. The processor will run at 4MHz, and the data, address, and control signals will change less frequently. For instance, the address lines will be active for the first cycle (about 250ns) out of 3 or more cycles the processor will use to execute an instruction. I guess from that the change rate would be more like 1.3 MHz.

Does that sound like I am heading for problems? Or are the frequencies low enough to just connect the busses throught the cable?

Thanks,

David

 

[Nigel Goodwin]

Does that sound like I am heading for problems? Or are the frequencies low enough to just connect the busses throught the cable?

I wouldn't have though that would cause any problems, if the processor has a 4MHz crystal it's probably running a fair bit slower than that anyway.

I'd happily use ribbon cables on PIC running at 20MHz, with 200nS per instruction - which is probably a LOT! faster than your board will be running.