User Manual

PROGRAMMING
3-7
Part No. 001-3422-003
C-Word calculation:
NA = 1095 (Decimal)
PA = 1
C-Word (Hex) = 94 47 80
B-Word calculation:
CN = 95 (Decimal from Table 3-3)
CK = 0000
CL = 00
PR = 10
B-Word (Hex) = 80 5F 2
A0-Word calculation:
When the D-Word is programmed with FMOD = 8 and NR = 875 as described above, the fractional increment
resolution is FCM ÷ FMOD = 20 kHz ÷ 8 = 2.5 kHz.
Where FCM = FREF ÷ NR = 17.5 MHz ÷ 875 = 20 kHz.
The total division ratio from the prescaler to the phase detector (with PR= “10”) is expressed as:
N = (NM1 + 2) x 64 + NM2 x 65 + (NM3 + 1) x 72
N’ = (NM1 + 1) x 64 + (NM2 + 1) x 65 + (NM3 + 1) x 72*
*When the fractional accumulator overflows the prescaler ratio = 65 x (64 + 1) and the total division ratio is
N’ = N + 1.
In the receive mode, the synthesizer is programmed to the 1
st
LO injection frequency which is 21.45 MHz
above the receive frequency (high side injection).
For this example, LO = 151.0175 + 21.45 MHz = 172.4675 MHz
N = LO ÷ FCM = 172.4675 ÷ .02 = 8623 {Integer part}
NM3 = [ INT{64 x FRAC {N ÷ 64} ÷ FMOD}] -1
= INT { (64 x 0.734375) ÷ 8} -1
= 5 - 1 = 4
NM2 = FMOD x FRAC {N ÷ FMOD}
= 8 x FRAC {1023 ÷ 8}
= 8 x 0.875
= 7