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:
![](https://cdn.hackaday.io/images/7295051547303172382.png)
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:
![](https://cdn.hackaday.io/images/3028101547303180859.png)
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.
![](https://cdn.hackaday.io/images/4234171547303265216.png)
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.
Discussions
Become a Hackaday.io Member
Create an account to leave a comment. Already have an account? Log In.