Manual

2
3 Definitions
The following give details of the terms used thoughout this document.
3.1 Fosc
This is the value of the Reference Oscillator in the radio. This is NOT
programmable and the value is not stored in EEPROM. Currently there are
two types used by the ST/SRn00 units:
12.8 and 14.85 MHz.
3.2 Fc
Fc is the Comparison Frequency used by the synthesizer in the radio. This is
a programmable parameter, but care should be taken if it is changed,
because the synthesiser hardware is optimized for certain values of Fc. The
Fc in use with the ST/SRn00 family vary for the different applications, but is
one of these discrete values:
5, 6.25, 10, 12.5 ,20 or 25 KHz
(refer to Wood & Douglas for the actual values allowed).
Fc is not directly stored as a number in the radio’s EEPROM. It is rather
indirectly stored as the “Rvalue” (see below).
3.3 Rvalue
This number is the result of the division:
Rvalue = Fosc / Fc
Since the ST/SRn00 family can have one of two Fosc: 12.8 or 14.85 MHz, the
possible Rvalues for the radio are:
If Fosc= 12.8MHz:
RR1(5) = 2560 (dec), A00 (hex)
RR1(6.25) = 2048 (dec), 800 (hex)
RR1(10) = 1280 (dec), 500 (hex)
RR1(12.5) = 1024 (dec), 400 (hex)
RR1(20) = 640 (dec), 280 (hex)
RR1(25) = 512 (dec), 200 (hex)