RFM64B Datasheet, PDF (44/75 Pages) List of Unclassifed Manufacturers – ISM TRANSCEIVER MODULE

ADVANCED COMMUNICATIONS & SENSING
RFM 64B
5.4. Buffered Mode
5.4.1. General Description
As illustrated in Figure 38, for Buffered mode operation the NRZ data to (from) the (de)modulator is not directly
accessed by the uC but stored in the FIFO and accessed via the SPI Data interface. This frees the uC for other
tasks between processing data from the RFM64B, furthermore it simplifies software development and reduces uC
performance requirements (speed, reactivity). Note that in this mode the packet handler stays inactive.
An important feature is also the ability to empty the FIFO in Stby mode, ensuring low power consumption and
adding greater software flexibility.
RFM64B
CONTROL
IRQ_0
IRQ_1
Data
Rx
SYNC
RECOG.
Tx
FIFO
(+SR)
SPI
CONFIG
DATA
NSS_CONFIG
NSS_DATA
SCK
MOSI
MISO
Datapath
Figure 38: Buffered Mode Conceptual View
Note that Bit Synchronizer is automatically enabled in Buffered mode. The Sync word recognition must be
activated by the user if needed.
5.4.2. Tx Processing
After entering Tx in Buffered mode, the module expects the uC to write into the FIFO, via the SPI Data interface, all
the data bytes to be transmitted (preamble, Sync word, payload...).
Actual transmission of first byte will start either when the FIFO is not empty (i.e. first byte written by the uC) or when
the FIFO is full depending on bit IRQParam_Tx_start_irq_0.
In Buffered mode the packet length is not limited, i.e. as long as there are bytes inside the FIFO they are sent.
When the last byte is transferred to the SR, /Fifoempty IRQ source is asserted to warn the uC, at that time FIFO
can still be filled with additional bytes if needed.
When the last bit of the last byte has left the SR (i.e. 8 bit periods later), the Tx_done interrupt source is asserted
and the user can exit Tx mode after waiting at least 1 bit period from the last bit processed by modulator.
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