MRF49XA Datasheet, PDF (37/102 Pages) Microchip Technology – ISM Band Sub-GHz RF Transceiver

MRF49XA
REGISTER 2-12: DRSREG: DATA RATE VALUE SET REGISTER (POR: 0xC623)
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-1
R/W-0
bit 8
R/W-0
DRPE
bit 7
R/W-0
R/W-1
R/W-0
R/W-0
DRPV<6:0>⁽¹⁾
R/W-0
R/W-1
R/W-1
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
bit 6-0
CCB<15:8>: Command Code bits
The command code bits (11000110b) are serially sent to the microcontroller to identify the bits to be
written in the DRSREG.
DRPE: Date Rate Prescaler Enable bit
1 = Enables the prescaler to obtain smaller values of expected data rates. The prescaler value when
enabled is approximately 1/8 of the actual data rate.
0 = Disables the prescaler
DRPV<6:0>: Data Rate Parameter Value bits⁽¹⁾
These bits represent the decimal value of the 7-bit parameter which is used to calculate the expected
data rate.
Note 1:
To calculate the expected data rate, use Equation 2-4. To calculate the DRPV<6:0> decimal value for a
given bit rate, use Equation 2-5. If the prescaler is not used, the data rates range from 2.694 kbps to
344.828 kbps. With the prescaler enabled, the data rates range from 337 bps to 43.103 kbps. The Slow
Clock Recovery mode requires more accurate bit timing when setting the data rate. Equation 2-6 is used
to calculate the data rate accuracy for Fast and Slow modes.
EQUATION 2-4:
DREx (kbps) = 10000/29 x (DRPV<6:0> + 1) x (1 + DRPE x 7)
where:
DRPV<6:0> is the Decimal Value from 0 to 127 and the Prescaler (DRPE) is ‘1’ (if on) or ‘0’ (if off).
EQUATION 2-5:
DRPV<6:0> = 10000/[29 x (1 + DRPE x 7) x DREx] – 1
where:
DREx is the Expected Data Rate.
EQUATION 2-6:
• Slow Mode Accuracy (SMA) = ΔDR/DR < 1/(29 x LN)
• Fast Mode Accuracy (FMA) = ΔDR/DR < 3/(29 x LN)
where:
LN is the longest number of expected ones or zeros in the data stream.
ΔDR is the difference in the actual data rate versus the set data rate in the transmitter.
DR is the expected data rate set using DRPV<6:0>.
© 2009 Microchip Technology Inc.
Preliminary
DS70590B-page 35