Digi XBee DigiMesh 2.4, Руководство пользователя

Страница: 36 / 157

Serial communication Serial flow control
XBee/XBee-PRO DigiMesh 2.4 RF Module User Guide 36
Serial flow control
The RTS and CTS device pins provide RTS and/or CTS flow control. CTS flow control signals the host to
stop sending serial data to the device. RTS flow control lets the host signal the device so it will not
send the data in the serial transmit buffer out the UART. Use the
D6 and D7 commands to enable RTS
and CTS flow control.
CTS flow control
CTS flow control is enabled by default; you can disable it with the D7 command. When the serial
receive buffer fills with the number of bytes specified by the FT parameter, the device de-asserts CTS
(sets it high) to signal the host device to stop sending serial data. The device re-asserts CTS when less
than FT-16 bytes are in the UART receive buffer; for more information, see
FT (Flow Control
Threshold) .
RTS flow control
If you send the D6 command to enable RTS flow control, the device does not send data in the serial
transmit buffer out the DOUT pin as long as RTS is de-asserted (set high). Do not de-assert RTS for
long periods of time or the serial transmit buffer will fill. If the device receives an RF data packet and
the serial transmit buffer does not have enough space for all of the data bytes, it discards the entire
RF data packet.