RXC101 Datasheet, PDF (22/33 Pages) RF Monolithics, Inc – Multi-channel High data rate Programmable

Automatic Frequency Adjust Register [POR=C6F7h]
Bit Bit Bit Bit Bit Bit Bit Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
1 1 0 0 0 1 1 0 AUTO1 AUTO0 RNG1 RNG0 STRB ACCF OFFEN AFEN
The AFA (Automatic Frequency Adjust) Register configures:
• Manual or Automatic frequency offset adjustment
• Calculation of the offset value and write to the Status Register
• Fine offset adjustment control
The AFA (Automatic Frequency Adjust) Register controls and configures the frequency adjustment range
and mode for keeping the transmitter and receiver frequency locked, providing for an optimal link. The
AFA may be manually controlled by an external processor by asserting a strobe signal to initiate a
sample, or may be setup for automatic operation. The AFA also calculates the offset of the transmit and
receive frequency. This offset value is included in the status register read and the AFA must be disabled
during the status read to ensure reporting good offset accuracy.
Bit [15..8] - Command Code: These bits are the command code that is sent serially to the processor that
identifies the bits to be written to the Automatic Frequency Adjust Register.
Bit [7..6] – Mode Selection: These bits select Automatic or manual operation. When set to Manual
operation, the RXC101 will take a sample when a strobe signal (See Bit [3]) is written to the
register. There are four modes of operation. See Table 11 below for configuration.
TABLE 11.
Automatic fOFFSET Mode
Mode Off
Run Once after Pwr-up
Keep offset during Rcv ONLY
Keep offset indep of VDI state
AUTO1
0
0
1
1
AUTO0
0
1
0
1
Mode Operation
Mode(0,1) – The circuit takes a measurement only once after power-up. This maximizes the distance
that can be achieved for a single link.
Mode(1,0) – When the Valid Data Indicator (VDI) pin is low, indicating poor receiving conditions, the
offset register is automatically cleared. Use this setting when receiving from several different
transmitters that are operating very close to the same frequencies.
Mode(1,1) – This setting is best used when receiving from a single transmitter. The measured offset
value is kept independent of the state of the VDI signal.
Bit [5..4] – Allowable Frequency Offset: These bits select the amount of offset allowable between
Transmitter and Receiver frequencies. The allowable range can be specified as in Table 12
below.
TABLE 12.
Freq Offset Range RNG1 RNG0
No Limit
0
0
+15*fres/-16*fres 0
1
+7*fres /-8*fres
1
0
+3*fres /-4*fres
1
1
22