STM7E1A

5/10

DECODING OF FUNCTIONAL MODE 1 (MODE = L)

When closing the main port local loop (Lm high), it is external system responsibility to ensure that the main

port has previously been disconnected from the line (Sc has to be high). There is no internal mechanism

to ensure this.

When closing the spare port local loop (Ls high), it is external system responsibility to ensure that the

spare port has previously been disconnected from the line (Sc has to be high). There is no internal

mechanism to ensure this.

DECODING OF FUNCTIONAL MODE 2 (MODE = H)

C = Closed

O=Open

C = Closed

O=Open

TEST MODE DESCRIPTION (MODE = 0, TEST = 1)

In order to test the main switches (4-point measurement), test modes are foreseen where the main

switches can be controlled independently from each other. One can enter in test mode by controlling the

Sc, Lm and Ls pins according to the following table.

The digital part and auxiliary switches can be tested in functional mode.

Note 1: Although there is an internal pull down in the TEST pin, an external hardware connection from TEST to GND is required on the board

to work in functional, mode.

Main Switches

Sc low

a closed, b open

Main port is connected to the line

Sc high

a open, b closed

Spare port is connected to the line

Auxiliary

Switches

Lm low

d open

Main port local loop open

Lm high

d closed

Main port local loop closed

Ls low

c open

Spare port local loop open

Ls high

c closed

Spare port local loop closed

INPUT

OUTPUTS

TEST/Sn

A_TX

B_TX

LO

C

HC

O

INPUTS

OUTPUTS

Sc

Lm

Ls

A_RX

B_RX

c

d

LLL

C

C

O

O

L

L

HC

OC

O

LHL

O

C

O

C

L

HHC

O

O

O

H

L

L

OCOO

Signification

Sc

Lm

Ls

A_TX closed

H

H

L

A_RX closed

L

H

L

B_TX closed

H

L

H

B_RX closed

L

L

H

B_TX & c closed

H

L

L

A_RX & d closed

L

L

L

All main switches open

HH

H

LH

H