EV8680 Datasheet, PDF (33/39 Pages) CML Microcircuits – Evaluation Kit

Evaluation Kit for CMX868
EV8680
1.6.8 BER Measurement
To allow the user to perform a Bit Error Rate Test (BERT) on the CMX868, the EF8680 firmware
contains a BERT routine. This facility is enabled using the test functions AT@F4 (Rx End) or AT@F5
(Tx End). Before selecting these functions the user must select the required protocol via the ATBn
command. Various bit mapped S-registers must also be modified to select the CMX868 configuration
used during the BERT.
The BERT routines have been designed for use with two EV8680 kits and a BER Datatester unit
(compatible with the EV8680 BER test pin timings, see below). The firmware only allows the user to set
up a single EV8680 board as the Tx or Rx end. The second EV8680 evaluation board(not supplied)
could be replaced with an alternative system (designed for use with the BER Datatester unit).
The EV8680 BERT is performed in synchronous mode and uses simple negotiation before data is
clocked in and out of the BER Datatester unit.
Hardware Setup
This function enables connection to BER Testers as follows:
TEST3 (J3 Pin 10) from BER Tester Tx Data O/P
TEST2 (J3 Pin 9) to BER Tester Tx Data Clock I/P
TEST1 (J3 Pin 8) to BER Tester Rx Data I/P
TEST0 (J3 Pin 7) to BER Tester Rx Data Clock I/P
The tester must be able to operate from an external clock. The timings of the clock provided from the
Evaluation board µC are as follows:
8-Bit Time
t_A
Rx Data
Clock O/P
Rx Data
O/P
1
0
1
0
0
1
1
0
Figure 5 Evaluation Board µC Rx Timing
The µC modifies the state of the Rx data output before taking the Rx clock pin high. Therefore, Rx data
is assumed to be clocked into the BER Datatester on the rising edge of Rx clock.
8-Bit Time
t_A
Tx Data
Clock O/P
Tx Data
I/P
10100110
Figure 6 Evaluation Board µC Tx Timing
© 2000 Consumer Microcircuits Limited
33
UM8680/2