B&B Electronics ZXT9-MB2A-KIT - Manual - Manual (Page 61)

Document Number: ZXTxRM-5110m
Page
61
The API operation option facilitates many operations such as the examples cited below:
• Transmitting data to multiple destinations without entering Command Mode
• Receive success/failure status of each transmitted RF packet
• Identify the source address of each received packet
To implement API operations, refer to API sections.
6.3.4 Flow Control
Input Buffer
When serial data received by modem, the data is stored in the input Buffer until it can be
processed.
Hardware Flow Control (CTS).
When the input buffer is 17 bytes away from being full; by
default, the modem de-asserts CTS (high) to signal to the host device to stop sending
data [refer to FT (Flow Control Threshold) and CS (GPO1 Configuration) Commands].
CTS is re-asserted after the Buffer has 34 bytes of memory available.
Software Flow Control (XON).
XON/XOFF software flow control can be enabled using
the FL (Software Flow Control) Command. This option only works with ASCII data.
How to eliminate the need for flow control:
• Send messages that are smaller than the input buffer size. The size of the input buffer
varies according to the packet size (PK parameter) and the parity setting (NB
parameter) used.
• Interface at a lower baud rate [BD (Interface Data Rate) parameter] than the RF data
rate (BR parameter).
Two cases in which the input Buffer may become full and possibly overflow
:
• If the serial interface data rate is set higher than the RF data rate of the modem, the
modem will receive data from the host faster than it can transmit the data over-the-air.
• If the modem is receiving a continuous stream of RF data or if the modem is
monitoring data on a network, any serial data that arrives on the modem is placed in
the Input Buffer. The data in the input buffer will be transmitted over-the-air when the
modem no longer detects RF data in the network.
Output Buffer
When RF data is received, the data enters the output buffer and is sent out the serial port
to a host device. Once the output buffer reaches capacity, any additional incoming RF
data is lost. The output buffer stores at least 2.1 KB.
Hardware Flow Control (RTS).
If RTS is enabled for flow control (RT Parameter = 2),
data will not be sent out the output buffer as long as RTS (pin 10) is de-asserted.
Software Flow Control (XOFF).
XON/XOFF software flow control can be enabled using
the FL (Software Flow Control) Command. This option only works with ASCII data.
Two cases in which the output buffer may become full and possibly overflow
:
• If the RF data rate is set higher than the interface data rate of the modem, the modem
will receive data from the transmitting modem faster than it can send the data to the
host.