Si1000/1/2/3/4/5
D7
D6
D5
D4
D3
D2
D1
D0
POR Def.
Add R/W
Function/
Description
79 R/W Frequency Hopping fhch[7] fhch[6] fhch[5] fhch[4] fhch[3] fhch[2] fhch[1] fhch[0]
Channel Select
00h
00h
7A R/W Frequency Hopping fhs[7]
Step Size
fhs[6]
fhs[5]
fhs[4]
fhs[3]
fhs[2]
fhs[1]
fhs[0]
23.3.4. Automatic State Transition for Frequency Change
If registers 79h or 7Ah are changed in either TX or RX mode, the state machine will automatically transition
the chip back to TUNE, change the frequency, and automatically go back to either TX or RX. This feature
is useful to reduce the number of SPI commands required in a Frequency Hopping System. This in turn
reduces microcontroller activity, reducing current consumption. The exception to this is during TX FIFO
mode. If a frequency change is initiated during a TX packet, then the part will complete the current TX
packet and will only change the frequency for subsequent packets.
23.3.5. Frequency Deviation
The peak frequency deviation is configurable from ±0.625 to ±320 kHz. The Frequency Deviation (Δf) is
controlled by the Frequency Deviation Register (fd), address 71 and 72h, and is independent of the carrier
frequency setting. When enabled, regardless of the setting of the hbsel bit (high band or low band), the
resolution of the frequency deviation will remain in increments of 625 Hz. When using frequency modula-
tion the carrier frequency will deviate from the nominal center channel carrier frequency by ±Δf:
f fd[8:0]625Hz
f
fd[8 : 0]
f = peak deviation
625Hz
f
fcarrier
Time
Figure 23.4. Frequency Deviation
The previous equation should be used to calculate the desired frequency deviation. If desired, frequency
modulation may also be disabled in order to obtain an unmodulated carrier signal at the channel center fre-
quency; see “Modulation Type” on page 251 for further details.
248
Rev. 1.0
SILICON [ SILICON ]
