Zilog Z80 homebrew computer rs232 problem

[Hugo Holden]

PS: One interesting thing on that votrax circuit I posted, notice the "poor man's" voltage level converters on the incoming signals from the RS-232 connector, feeding the signals via 39k resistors into the input of 4049 cmos logic gates. This works, because of the input protection diodes in the IC that limit the input pin voltage excursions to a diode voltage drop above +5V and below gnd.

 

[Sendraz]

Hi, sorry for the delay. I was working on a full schematic of my z80 board. Here it is.

If you could post your exact schematic around the 6850 UART might help.

Sometimes if I run into trouble getting an IC running as expected, as well as looking at the data sheet, I look at an example circuit that is known to work using it. This helps to check every pin is used properly.

The only circuit I have with a 6850 in it , is the Votrax TNT, so I have attached that, it shows how this IC is normally hooked up with a CPU & Baud rate generator and a line driver IC.

 

[Roger Wilco]

Well, i was thinking about getting an z80 SIO, but for some reason thought that the 6850 will be good, because some other homebrew z80 projects used it

How do you think: why Hitachi has two lines of its HD64180 — one for Motorola peripherals and the other one for Zilog family? Because they wanted to raise their manufacturing costs? Honestly, although probably that chip can be „raped” to work in your SBC somehow, still the better idea would be to employ Z80 SIO.
BTW: by using 64180 you could get 2-chip SBC: fitted just with the „main one” and memory chip.