User's Guide

Table Of Contents
Operation SPI operation
XBee/XBee-PRO S2C 802.15.4 RF Module User Guide
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If the device sends data out the UART when RTS is de-asserted (set high) the device could send up to
five characters out the UART port after RTS is de-asserted.
Cases in which the DO buffer may become full, resulting in dropped RF packets:
1. If the RF data rate is set higher than the interface data rate of the device, the device may
receive data faster than it can send the data to the host. Even occasional transmissions from a
large number of devices can quickly accumulate and overflow the transmit buffer.
2. If the host does not allow the device to transmit data out from the serial transmit buffer due to
being held off by hardware flow control.
Asynchronous Parameters
Asynchronous communication over a UART is configured with a start bit, data bits, parity, stop bits,
and baud rate. Out of these, only parity and baud rate are configurable on the device for 802.15.4. This
means that the connecting micro-controller must match the the start bits (1), the data bits (8), and
the stop bits (1) of the device for proper communication.
Parity
Use the NB command to configure parity; see NB (Parity).
SPI operation
This section specifies how SPI is implemented on the device, what the SPI signals are, and how full
duplex operations work.
SPI signals
The XBee/XBee-PRO S2C 802.15.4 RF Module supports SPI communications in slave mode. Slave mode
receives the clock signal and data from the master and returns data to the master. The SPI port uses
the following signals on the device:
Signal
SMT pin
#
SMT applicable AT
command
TH Pin
#
TH applicable AT
command
SPI_MOSI (Master out,
Slave in)
16
P6
11 D4
SPI_MISO (Master in,
Slave out)
17
P5
4 P2
SPI_SCLK (Serial clock)
14
P8
18 D2
SPI_SSEL (Slave select)
15
P7
17 D3
SPI_ATTN (Attention)
12
P9
19 D1
By default, the inputs have pull-up resistors enabled. Use the PR command to disable the pull-up
resistors. When the SPI pins are not connected but the pins are configured for SPI operation, then the
device requires the pull-ups for proper UART operation.
Signal description
SPI_MISO:When SPI_CLK is active, the device outputs the data on SPI_MISO at the SPI_CLK rate. If
there are other SPI slave devices connected to the same SPI master, then the SPI_MISO output from