EV6240 datasheet(30/47 Pages) CMLMICRO

30 / 47 page

Evaluation Kit for CMX624/CMX644A

EV6240

UM6240/3

1.6.5

Evaluation Tests

1.6.5.1 BER Measurement (Not available in the current firmware revision).

To allow the user to perform Bit Error Rate Testing (BERT) the EF6240 firmware contains a BERT

routine. This facility requires the user to put the evaluation board into Test Mode (AT@E1) and modify

the BER Measurement Set Up (AT@Tn) to the appropriate configuration. The BERT routine can be

configured to operate in one of two ways; with a single on-board Modem connected to an external

simulator/modem, via the 2 or 4-wire line interfaces;

or simply by connecting the two on-board

Modems together via the 2 or 4-wire line interfaces.

Note, the BERT routine is performed in synchronous mode and uses a preamble and sync byte when

it begins to allow the µC firmware to synchronise with the start of the bit stream.

When the

configuration set up is complete BERT can commence by entering the AT@F1 command.

The BER

Tester should be started before the user enters the AT@F1 command to ensure bit synchronisation is

achieved.

Hardware Setup

This function enables connection to BER Testers as follows:

TP42 (PIC16C77 µC Pin 19) to BER Tester Tx Data O/P

TP43 (PIC16C77 µC Pin 20) to BER Tester Tx Data Clock I/P

TP44 (PIC16C77 µC Pin 21) to BER Tester Rx Data I/P

TP45 (PIC16C77 µC Pin 22) 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:

1 Byte Time

Tx Clock

Rx Clock

Figure 7 Evaluation board µC clock outputs

Times t

A and tB vary as the clocks are adjusted to fit the exact byte periods of the evaluation devices.

Data is assumed to be clocked in and out of the Tester on the rising edge of either Rx or Tx clock.

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