MRF49XAT-I-ST Datasheet, PDF (70/102 Pages) Microchip Technology – ISM Band Sub-GHz RF Transceiver

MRF49XA
3.18 RX FIFO Buffered Data Read
In the Receive Operating mode, the incoming data is
clocked into a 16-bit FIFO buffer. The receive pin
function configuration required for the FIFO operation
is given in Table 3-4. The FIFOEN bit is in the
GENCREG register and enables the receive FIFO. The
receiver starts to fill the FIFO when the FINTDIO bit and
the synchronous pattern recognition circuit indicates
the potential real incoming data. This prevents the
FIFO from being filled with noise and avoids the
overloading on the external microcontroller.
The internal synchronous pattern and the pattern
length are user-programmable. If the Chip Select (CS)
pin is low, the data bits on the SDI pin are shifted into
FIGURE 3-18:
RECEIVER FIFO READ
the device on the rising edge of the clock on the SCK
pin. The serial interface is initialized every time if the
CS signal is high. Figure 3-18 shows a simple receiver
FIFO read over SPI lines.
In general, MRF49XA registers are read only. The
RXFIFO and the chip status can be read. During write
only appropriate byte is written to the desired register.
Hence it is not desired to read/write all registers and
there is no way reading back any of the other registers.
To test the SPI interface lines, the best is to set the LBD
(Low Battery Detector) threshold below the actual VDD
and the device must generate an interrupt.
CS
SCK
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
SDI
SDO
TXRXFIFO
(TX/RX mode)
Received Bits Out
MSB
LSB
Note: The transceiver is in Receive (RX) mode when the RXCEN bit is set using the PMCREG .
DS70590C-page 70
Preliminary
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