25-04-2024, 09:56 AM
David used a crystal for each modulator chip.
In the Vol modulator I did also. While not impossible there was no convenient way of getting a clock from the PIC I used and space wasn't a problem on the PCB.
In the Hedghog L resources were limited in the FPGA and the clock generation for the modulators was farmed out to the PIC. The PIC used was chosen as it has a reference clock output which is used to drive the modulators. This arrangement was kept for subsequent Hedghog's.
Why I used a capacitor instead of a resistors? At the time I had no idea how Darryl or anyone else did it. Looking at the diagram in the data sheet there is a capacitor in series with the crystal. So I figured it was the way to go. Also a capacitor would isolate any DC conditions on that pin from the clock.
Frank
In the Vol modulator I did also. While not impossible there was no convenient way of getting a clock from the PIC I used and space wasn't a problem on the PCB.
In the Hedghog L resources were limited in the FPGA and the clock generation for the modulators was farmed out to the PIC. The PIC used was chosen as it has a reference clock output which is used to drive the modulators. This arrangement was kept for subsequent Hedghog's.
Why I used a capacitor instead of a resistors? At the time I had no idea how Darryl or anyone else did it. Looking at the diagram in the data sheet there is a capacitor in series with the crystal. So I figured it was the way to go. Also a capacitor would isolate any DC conditions on that pin from the clock.
Frank
