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5.3
Bank select inputs
ProgRock contains stored frequencies for 8 banks of frequencies, with 3 output frequencies in each bank.
If you wish to use this feature, you should select the bank you want to use, using the three input signals
Sel 0, Sel 1 and Sel 2. Immediately the setting on these three input signals changes, ProgRock will
reprogram the Si5351A to the frequencies stored in its non-volatile EEPROM memory.
By default, if you leave the signals disconnected, Bank 0 is used.
These signals have the internal pullup activated within the microcontroller. The signals are active-low.
“Low” voltage means 0V (ground), “High voltage” means 5V – or just disconnect completely (since the
internal pull-ups will make the pin high).
The mapping of input signals to bank selected, is ordinary binary. For clarity, the mapping is listed in the
table below.
Sel 2
Sel 1
Sel 0
Bank
High
High
High
0
High
High
Low
1
High
Low
High
2
High
Low
Low
3
Low
High
High
4
Low
High
Low
5
Low
Low
High
6
Low
Low
Low
7
The frequency banks could be used for many purposes. You may wish to program different “crystal”
frequencies for different bands in your radio, for example; or for upper/lower sideband. You could also use
one of the Bank inputs as a “key” signal to enable the frequency output. For example imagine
programming the frequencies you want, in Bank 0. Then use the “Sel 0” input as a “keying” signal.
Assuming you have left all three Bank 1 frequencies as 0Hz, the effect will be that when Sel 0 is taken
Low, the frequency outputs are all disabled. Of course, you could reverse Bank 1 and Bank 0 in this
example, if you want the Sel 0 “keying” input to be active high instead.
ProgRock allows you a LOT of flexibility!
5.4
Signal outputs
The raw outputs of the Si5351A Synth IC in the synth module kit are available in two places. Firstly, there
are pads on the Si5351A Synth kit where you may solder edge-type SMA connectors if you wish.
Secondly, if you prefer, there are also output pins on the connector, as shown previously in the connection
diagram.
The outputs are 3.3V peak-peak squarewaves, with 50-ohm impedance. The maximum drive current
setting in the Si5351A register configuration is used.
Note that if the GPS discipline option is used, by connecting a GPS 1pps timing signal to the 1pps input
pin, then the Clk2 output will be used by the microcontroller to measure the 27MHz reference crystal
oscillator frequency, to permit calibration and drift correction. In this case you should not use or connect
anything to the Clk2 output.
