UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

TonyDuell · 8th Jan 2018, 6:11 pm

I do quite enjoy tracing out schematics, but only for devices I own. So you will not convnce me to trace out the diagrams for this unit, unless somehow I get one.

As for the microcontrollers. One is in the keyboard, and is clearly for scanning the keyboard and probably providing a serial link to the rest of the unit. It is also not uncommon to have 2 microcontrollers in a printer, basically one to operate the stepper motors (carriage and paper feed) and one to fire the printhead pins/elements, with other functions spread between them. Look at the circuit of the venerable Epson MX80, for example.

I agree a logic analyser would be useful, as I said in another thread I use them a lot. I have no direct experience of the USB units you use with a PC, but I have indirect experience in that I have been helping a friend in another country debug an early personal computer (HP9830, bit serial processor built from TTL) and that's what he used. It was certainly adequate for that and he knew how to use it to capture the signals I needed to see.

8th Jan 2018, 6:11 pm	#41
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,213	Re: 8085 processor questions I do quite enjoy tracing out schematics, but only for devices I own. So you will not convnce me to trace out the diagrams for this unit, unless somehow I get one. As for the microcontrollers. One is in the keyboard, and is clearly for scanning the keyboard and probably providing a serial link to the rest of the unit. It is also not uncommon to have 2 microcontrollers in a printer, basically one to operate the stepper motors (carriage and paper feed) and one to fire the printhead pins/elements, with other functions spread between them. Look at the circuit of the venerable Epson MX80, for example. I agree a logic analyser would be useful, as I said in another thread I use them a lot. I have no direct experience of the USB units you use with a PC, but I have indirect experience in that I have been helping a friend in another country debug an early personal computer (HP9830, bit serial processor built from TTL) and that's what he used. It was certainly adequate for that and he knew how to use it to capture the signals I needed to see.