805U Radio Modem Module
User Manual
Page
50
©
November 2004
6.2.2
Bit Error Rate Test (BER)
BER may be tested in one direction by typing AT&T0 (BER master) at the sending unit and
typing AT&T1 (BER slave) at the receiving unit. The sending unit will repeatedly send
pseudo-random frames, and the receiving unit will check these frames for errors. If a
terminal is connected to the sending unit, the pseudo-random data is displayed as it is
transmitted. If a terminal is connected to the receiving unit, then the test results are
displayed.
An example of the receiving unit’s display is here.
Test
Errors
Extra
Level
TotErr
TotMissed
TotTest
109
0
0
-77dBm
3
0
109 kbit
Test
-
the sequence number of the last received frame
Errors
-
the number of bit errors in the last received frame
Extra
-
any extra characters at the end of the frame (negative numbers indicate
frame dropped out early)
Level
-
the RSSI level when the frame was received.
TotErr
-
The total errors received during this test.
TotMissed
The number of missed frames during this test
TotTest
-
The total number of bits sent (in 1000’s)
Occasionally during testing, the following may be displayed:
Test
Errors
Extra
Level
TotErr
TotTest
Bad Header
This indicated that the header information has been corrupted. Corrupted headers do not
contribute to the bit errors, which are calculated only on the 1,000 bit frame.
BER testing may also be performed in both directions simultaneously. In this case, a remote
module is set up to Transparent mode repeater operation (set Group address and Unit address
both to 1) and the BER test is performed on the local module using the command AT&T2
(loopback Bit Error Test). In this case, the display is identical to the display on the BER slave
unit above, but the displayed bit errors are a total for the round trip, so will be the sum of the
bit errors in both directions. This test is generally the easiest to perform with one person -
the remote module can be set as a repeater, and the full test can then be carried out from the
other module. During this test, disconnect the serial cable to any host device at the repeater.
The BER test will automatically end if a test time has been entered at S8 register (refer
Appendix A). If S8 has a zero value (default), the timer is inactive and the BER test will
continue until manually stopped.
The BER test can also be initiated by the configuration switches in the end-plate - see
section 4.7.
6.2.3
On-line diagnostics
Some diagnostic values may be read by a host device, using AT commands. These values
include the radio signal strength of the last message received (ATS9?) and the reason for the
communication link resetting in controlled mode (ATS12?) - refer Appendix 1.
