MRF49XA Datasheet, PDF (23/102 Pages) Microchip Technology – ISM Band Sub-GHz RF Transceiver

MRF49XA
REGISTER 2-3: AFCCREG: AUTOMATIC FREQUENCY CONTROL CONFIGURATION REGISTER
(POR: 0xC4F7)
R/W-1
bit 15
R/W-1
R/W-0
R/W-0
R/W-0
CCB<15:8>
R/W-1
R/W-0
R/W-0
bit 8
R/W-1
R/W-1
AUTOMS<1:0>
bit 7
R/W-1
R/W-1
ARFO<1:0>
R/W-0
MFCS
R/W-1
HAM
R/W-1
FOREN
R/W-1
FOFEN
bit 0
Legend:
R = Readable bit
-n = Value at POR
r = reserved bit
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 15-8
bit 7-6
bit 5-4
bit 3
bit 2
bit 1
CCB<15:8>: Command Code bits
The command code bits (11000100b) are serially sent to the microcontroller to identify the bits to be
written in the AFCCREG.
AUTOMS<1:0>: Automatic Mode Selection bits (for AFC)
These bits select the operation type (automatic/manual) for performing AFC based on the status of
the MFCS bit.
11 = Keeps offset independent for the state of the DIO signal
10 = Keeps offset only while receiving (DIO = High)
01 = Runs and measures only once after each power-up cycle
00 = Auto mode off (controlled by microcontroller)
ARFO<1:0>: Allowable Range for Frequency Offset bits
These bits select the offset range allowable between transmitter and receiver frequencies.
11 = +3 FRES to -4 FRES⁽¹⁾
10 = +7 FRES to -8 FRES
01 = +15 FRES to -16 FRES
00 = No restriction
MFCS: Manual Frequency Control Strobe bit
This bit is the strobe signal which initiates the manual frequency control sample to calculate the offset error.
1 = A sample of a received signal is compared with a receiver Local Oscillator (LO) signal and an offset
error is calculated. If bit 1 is enabled, the value is stored in the Offset register of the AFC block.⁽²⁾
0 = Ready for the next sample
HAM: High-Accuracy (Fine) Mode bit⁽³⁾
1 = Switches the Frequency Control mode to High-Accuracy mode
0 = Frequency Control mode works in regular mode
FOREN: Frequency Offset Register Enable bit
1 = Enables the offset value calculated by the offset sample. The offset value is added to the
frequency control word of the PLL which tunes the desired carrier frequency.
0 = Denies the addition of the offset value to the frequency control word of the PLL
Note 1:
2:
3:
The FRES is the frequency tuning resolution for each band. The FRES for each band is as follows:
433 MHz = 2.5 kHz
868 MHz = 5 kHz
915 MHz = 7.5 kHz
The offset error value is stored in the Offset register (FOREN bit should be enabled) in the AFC block and
is added to the frequency control word of the PLL. Reset this bit before initiating another sample.
In High-Accuracy (Fine) mode, the processing time is twice the regular mode, but the uncertainty of the
measurement is significantly reduced.
© 2009 Microchip Technology Inc.
Preliminary
DS70590B-page 21