Dual Clock: 3 pads under 74LS393 (U4)

[Michelle Lawson]

I see from the schematic that these are pads going to three of the Q outputs of U4, but what is their intended purpose? Thanks

[Spencer Owen]

The clock divider circuit generates quite a few frequencies.  Not all of them will result in a valid baud rate from the serial port though, which is why they haven't been routed out to the jumpers at the top of the module. In fact, they're unlikely to be of any use at all - however, just in case you really really need them, you can at least solder a wire in there if necessary.

Similarly, under the '138 on the compact flash module are pads that would put the CF on different ports. Again, it is unlikely that you will ever need to do that, but those pads are there just in case.

Spencer

On 17/11/2025 19:44, Michelle Lawson wrote:

I see from the schematic that these are pads going to three of the Q outputs of U4, but what is their intended purpose? Thanks --
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[Michelle Lawson]

Gotcha. Figured I'd ask and not assume. Thanks