Okay, the Issue 3 is here...

A project log for OMEN Kilo

As simple as possible single-board computer with the 6809 / 6309 CPU.

Martin MalyMartin Maly 01/12/2019 at 14:300 Comments

Issue 3 has one and only reason...

I have a lot of 6809EP / 6309EP CPUs. Unfortunately, some sellers has a 6809EP, but marked as a 6809P. The biggest difference between E and nonE version is that nonE version has a built-in oscillator and pins E and Q are outputs. The E version has no oscillator and E / Q pins are inputs. You have to generate these quadrature clock signals outside.

There are a lot of computers with the 6809EP CPUs. Their authors often uses an external oscillator and a quadrature divider, based on dual J-K FFs, typically 74LS72:

But the 74LS72 is a little difficult to obtain. So I have designed a similar device, but based on dual RS FF, i.e. 74HC(T)74:

I have used two invertors (1/3 of the 74HC04) as a crystal oscillator and design a dual purpose PCB, code name "Issue 3". The added ICs made a little bigger PCB, so I decided to place the PIA 6821 on the board too. So you can see these new additions on the right side.

The last minor update is that PCB has four mounting holes at the corners. I believe this PCB will be available soon at my shop on Tindie.