EV8680 datasheet(33/39 Pages) CMLMICRO

33 / 39 page

Evaluation Kit for CMX868

EV8680

UM8680/2

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

Rx Data

Clock O/P

Rx Data

O/P

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

Tx Data

Clock O/P

Tx Data

I/P

Figure 6 Evaluation Board µC Tx Timing

EV8680 Datasheet(PDF) 33 Page - CML Microcircuits