Chapter 5 Diagnostics
MX-2100/2104
Installation and Operation Manual
5-14
Diagnostic Tests
PRBS Transmission
The PRBS transmission function is used to provide a test signal to a channel of a
data I/O module. By activating a local or remote main link loop, or a remote
channel loop (or by connecting an external loop) while PRBS transmission is
activated, this function can also be used to obtain a qualitative evaluation of data
transmission without using external test equipment.
Data transmission is checked by applying a 2
9
- 1 (511) bit pseudo-random
sequence generated by an internal test sequence generator to the input of the
tested channel transmit path. The transmitted data is returned by means of a loop
somewhere along the data path (e.g., by connecting a remote channel loop if
downloading is enabled, or a local main link loop) to the receive path of the
module. The received signal is routed to a test sequence evaluator. The evaluator
compares the received data, bit by bit, to the original data and detects any
difference (bit error). The output of the evaluator is sampled during module
polling, to check whether errors were detected in the interval between consecutive
pollings.
The test results are displayed as follows:
•
On the LCD located on the MX-2100 front panel, the result is displayed either
as GOOD (no error has been detected during the last interval), or BAD (at
least one error has already been detected). Note that if no loop is present
along the signal path, the BAD result is expected, and does not indicate any
problem.
•
On a supervision terminal, the test results are displayed as a number in the
range of 0 (no errors detected during the current measurement interval)
through 9999. The number of errors is accumulated from the activation of the
PRBS transmission.
During PRBS transmission, the tested channel is disconnected from the user data
equipment, and the DSR line is turned off. At any time, PRBS transmission can be
activated on only one channel of each data I/O module installed in the MX-2100
unit.
BERT Testing
The BERT test is used to evaluate data transmission through a selected channel of a
data I/O module without using external test equipment. The BERT test can be
activated only when the downloading function is enabled, and the link to the
remote MX-2100 operates normally.
The BERT test is similar to the PRBS transmission test, except that before the
evaluation of the received data starts, a remote channel loop is activated. This
should cause the sequence to be transmitted along the full path. The test results
are displayed as for PRBS transmission.
As for PRBS transmission, the BERT test can be activated on only one channel of
each data I/O module installed in the MX-2100 unit, the tested channel is
disconnected from the user data equipment, and its DSR line is turned off.