Operation
RFI-9256 Radio Modem User Manual
Page 20 of 109
5. Operation
5.1 Serial Port Operation
The RFI-9256 radio has two data communications equipment (DCE) RS-232 serial ports provided on a
single DB25 connector. The DB25 pin out can be found in Appendix A.3on page 60.
The main port supports:
TX, RX, and GND.
RTS and DTR inputs.
CTS and DCD outputs.
While the auxiliary port supports:
TX, RX, and GND.
Both main and auxiliary serial ports have internal 4096 byte buffers on both transmit and receive interfaces.
This configuration is shown in Figure 6.
4096 byte output buffer
4096 byte input buffer
TX Line (input from DTE)
RX Line (output to DTE)
Input to RF /
internal processing
Output from RF /
internal processing
Figure 6: Buffering scheme on the RFI-9256
This serial port buffering scheme has a number of ramifications on the RFI-9256 operation:
No preamble is required to account for radio turn-on time.
If the data cannot be transmitted over-the-air, it will be buffered until the transmitter is ready.
If the data terminal equipment (DTE) is not ready for data, the RFI-9256 can buffer that data until
the DTE is ready.
5.1.1 Configuration
Both main and auxiliary serial ports support the configuration settings shown in Table 5.
Main -> Serial Port
