X09-019PKC-RA Digi International/Maxstream, X09-019PKC-RA Datasheet - Page 13

• Manufacturer Part Number: X09-019PKC-RA
• Description: MOD RF 900MHZ 19.2K RS232/485
• Manufacturer: Digi International/Maxstream
• Series: XStream™r

Specifications of X09-019PKC-RA

• Function: Transceiver, Modem
• Modulation Or Protocol: FHSS
• Frequency: 902MHz ~ 928MHz
• Applications: General Purpose
• Interface: RS-232, RS-485
• Sensitivity: -110dBm
• Power - Output: 20dBm
• Data Rate - Maximum: 20 kbps
• Voltage - Supply: 5V
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

© 2006 MaxStream, Inc. Confidential & Proprietary
XStream‐PKG‐R™ RS‐232/485 RF Modem – Product Manual v5.x00 [2006.02.24]
3.1.3. Flow Control
DI (Data In) Buffer and Flow Control
DO (Data Out) Buffer and Flow Control
How to eliminate the need for flow control:
Two cases in which the DI Buffer may become full and possibly overflow:
Two cases in which the DO Buffer may become full and possibly overflow:
Figure 3.2. Internal Data Flow Diagram
When serial data enters the XStream Modem through the DI Pin, then the data is stored in the DI
Buffer until it can be transmitted.
When the RO parameter threshold is satisfied (refer to Transmit Mode [p14] and Command
Descriptions [p25] sections for more information), the modem attempts to initialize an RF
connection. If the modem is already receiving RF data, the serial data is stored in the modem’s
DI Buffer. If the DI buffer becomes full, hardware or software flow control must be implemented
in order to prevent overflow (loss of data between the host and XStream RF Modem).
1.
2.
1.
2.
Hardware Flow Control (
default, the modem de-asserts (high)
to the FT (Flow Control Threshold) and CS (DO2 Configuration) commands].
after the DI 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.
When RF data is received, the data enters the DO buffer and is then sent out the serial port to a
host device. Once the DO Buffer reaches capacity, any additional incoming RF data is lost.
1.
2.
Hardware Flow Control (
not be sent out the DO Buffer as long as
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.
Send messages that are smaller than the DI buffer size. The size of the DI buffer varies
according to the packet size and parity setting used.
Interface at a lower baud rate (BD Command) than the fixed RF data rate.
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 DI pin is placed in the DI Buffer. The data in
the DI buffer will be transmitted over-the-air when the modem no longer detects RF data in
the network.
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.
If the host does not allow the modem to transmit data out from the DO buffer because of
being held off by hardware or software flow control.
(The five most commonly‐used pin signals are shown.)
). When the DI buffer is 17 bytes away from being full; by
). If
is enabled for flow control (RT Parameter = 2), data will
to signal to the host device to stop sending data [refer
is de-asserted.
is re-asserted
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