Texas Instruments CC2500 - Page 65

CC2500
S
WRS040
C
Page
65
of
89
0x0B: FSCTRL1
–
Frequency
S
ynthesizer
C
ontrol
Bit
Field Name
Reset
R/W
Description
7:5
Reserved
R0
4:0
FREQ_IF[4:0]
1
5
(0x0
F
)
R/W
The desired IF frequency to employ in RX. Subtracted from FS
base frequency in R
X and controls the digital complex mixer in
the demodulator.
IF
FREQ
f
f
XOSC
IF
_
2
10


The default va
lue gives an IF frequency of 381
kHz, assuming
a 26.0 MHz crystal.
0x0C: FSCTRL0
–
Frequency Synthesizer Control
Bit
Field Name
Reset
R/W
Description
7:0
FRE
QOFF[7:0]
0 (0x00)
R/W
Frequency offset added to the base frequency before being
used by the FS. (2
’
s
complement).
Resolution is F
XTAL
/2
14
(1.59
-
1.65 kHz); range is ±202 kHz to
±210 kHz, dependent of XTAL frequency.
0x0D: FREQ2
–
Frequency Control Word
, High Byte
Bit
Field Name
Reset
R/W
Description
7:6
FREQ[23:22]
1 (01)
R
FREQ[23:22] is always binary 01 (the FREQ2 register is in the range 85 to
95 with 26
-
27 MHz crystal)
5:0
FREQ[21:16]
30
(0x1E)
R/W
FREQ[23:0] is the base frequency for the frequenc
y synthesiser in
increments of F
XOSC
/2
16
.


0
:
23
2
16
FREQ
f
f
XOSC
carrier


0x0E: FREQ1
–
Frequency Control Word, Middle Byte
Bit
Field Name
Reset
R/W
Description
7:0
FREQ[15:8]
196 (0xC4)
R/W
Ref. FREQ2 register
0x0F: FREQ0
–
Frequency Control Word, Low Byte
Bit
Field Name
Reset
R/
W
Description
7:0
FREQ[7:0]
236 (0xEC)
R/W
Ref. FREQ2 register