The 1GHz prescaler chip takes a high frequency signal and outputs a f/64 square wave.
By including a switch (S3) and a 50 ohm resistor it is possible to switch in a prescaler device to drive SCLK/Y2 (pin 33) on Spock.
Spock can then be set to route this through to the PIC via Event 1 in Trigger Source R7 for counting, giving us a means of measuring frequencies up to 1 GHz.
S3 switches in the prescaler with a 50 ohm terminator to BNC CH-B. This has other benefits. It means that we can use Channel B as a 50 ohm terminated input.
For example, channel B with S3 on could be used as a Ethernet cable terminator with the ability to sample the network traffic for display on a PC.
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