Rev. 8/28/03

SP3508 Evaluation Board Manual

© Copyright 2003 Sipex Corporation

9

USING THE EVALUATION BOARD: Continued

Driver/Receiver Remote Loopback

The following example uses the ST driver

looped back into the TxC receiver. Use the

3 bit decoder to configure the SP3508 for the

desired protocol. Connect a jumper cable

between the ST(a) pin and the TxC(a) pin. If

your mode select is set for a differential

driver/receiver, then also connect a jumper

cable between the ST(b) pin and the TxC(b)

pin. The next step is to connect a signal

generator to the ST input pin through BNC

input connector. The signal generator out-

put must be a TTL-level output at a fre-

quency within the acceptable range of the

driver mode under test. Be sure that the

jumper settings of STEN signal and TxCEN

signal are set to enable the ST driver and

TxC receiver. The driver outputs are now

connected back to the receiver inputs so

that the driver input to receiver output can be

examined. This configuration is similar for

all other drivers.

Driver/Receiver Local Loopback

The SP3508 has the ability to provide an

internal loopback. This feature is invoked by

a logic “0” on the /LOOPBACK pin. The

driver input and receiver output characteris-

tics adhere to the appropriate specifications

outlined in the datasheet under loopback

conditions. The /LOOPBACK pin has an

internal pull-up resistor so that the SP3508

defaults to normal operation during power-

up or if the pin is left floating.

DCE DTE selectable configuration

• Configure the decoder for the desired

mode.

• The SP3508 evaluation board has jumper

setup to allow for the evaluation of a select-

able DCE DTE configuration.

• Set the STEN and RRCEN to Logic “0”.

This will disable the ST and RRC driver

outputs. (Refer to the Jumper Setting Guide

in the next section)

• Set the /TxCEN and /RRTEN to Logic “1”.

This will disable the TxC and RRT receiver

inputs. (Refer to the Jumper Setting Guide in

the next section)

• Use an external wire to tie the ST driver

outputs to the TxC Receiver inputs.

• Use an external wire to tie the RRC driver

outputs to the RRT receiver inputs.

• To enable a DTE configuration, set the

STEN and RRCEN to Logic “1”. Be sure the

TxC and RRT receivers are disabled by

setting the /TxCEN and /RRTEN to Logic

“1”. (Refer to the Jumper Setting Guide in

the next section)

• To enable a DCE configuration, set the /

TxCEN and /RRTEN to Logic “0”. Be sure to

disable the ST and RRC driver outputs by

setting the STEN and RRCEN to Logic “0”.

(Refer to the Jumper Setting Guide in the

next section)

System Level Evaluation

• Use DB-25 Connector if the evaluation

board is configured as a DTE for EIA-530

pinout. In order to connect to other DCE

equipment or network analyzers ( i.e. the

TTC Firebird 6000A), the RxC receiver out-

put must be looped back to the TxCE driver

input. The RxD output can also be looped

back to the TxD input.

• If connecting the evaluation board to a

microcontroller such as the Motorola

MC68360, jumper wires of the driver inputs

and receiver outputs must connect to the

uC’s appropriate pins.