a number of parameters need to be worked out;
the 12mhz tcxo is divided by 16 (ic101) to provide a 750khz reference frequency. this reference frequency is sampled and divided by the 'reference division rate' to determine the channel spacings.
reference division rate - 750khz/12.5khz = 60 = c30 in reversed hex as used by the key (see tx(r) & rx(r) in the table below).
reference division rate - 750khz/10khz = 75 = b40 in reversed hex as used by the key (see tx(r) & rx(r) in the table below).
each address code always starts with f i.e. f* f* f* so that for the reference division rate for 12.5khz c30 works out to be fc f3 f0.
d = basic division rate = frequency of operation / 12.5
d = prescaler division rate fixed at 64
n = number of complete divisions
r = remainder of the basic division rate
'n' & 'a' are calculated using the following equation; d = ( n x d ) + a / works out to the following in the example below
11.602 = (0.181 x 64) + 0.018
a tx frequency of 145.025mhz = 145.025/12.5 = 11.602 = d then divided by d (fixed at 64)
11.602/64 = 0.18128125 = 0.181 number of complete divisions = n = 181 converted into hex and reversed = 5b0 (see tx(n) in the table below).
0.181x64 = 11.584-11.602 = 0.018 = a = remainder of the basic division rate
18 converted into hex and reversed = 21 (see tx(a) in the table below).
receive is similar but 21.6mhz has to be taken off the rx frequency
a rx frequency of 145.625mhz = 145.625-21.6/12.5 = 9.922/64 = 0.15503125
0.155 number of complete divisions = n = 155 converted into hex then reversed b90 (see rx(n) in the table below).
0.155x64 = 9.92-9.922 = 0.002 = a = remainder of the basic division rate
2 converted into hex and reversed = 20 (see rx(a) in the table below).
key 2732 eprom coding
channel #1 address 0 1 2 3 4 5 6 7 8 9 a b c d e f
tx(a) tx(n) tx(r) rx(a) rx(n) rx(r)
channel data - example 145.025 tx 145.625 rx f2 f1 f5 fb f0 fc f3 f0 f2 f0 fb f9 f0 fc f3 f0
channel #2 address 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
tx(a) tx(n) tx(r) rx(a) rx(n) rx(r)
channel data - example 145.050 tx 145.650 rx f4 f1 f5 fb f0 fc f3 f0 f4 f0 fb f9 f0 fc f3 f0
