Application circuit

STM7E1

4/16

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.

C = Closed

O = Open

C = Closed

O = Open

Table 2.

Decoding of functional Mode 1 (Mode = L)

Switches

Status

Description

Main

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

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

Table 3.

Decoding of functional Mode 2 (Mode = H)

Input

Outputs

TEST/Sn

A_TX

B_TX

LO

C

HC

O

Table 4.

Decoding of functional Mode 2 (Mode = H)

Inputs

Outputs

Sc

Lm

Ls

A_RX

B_RX

c

d

LLL

C

C

O

O

LL

H

C

O

C

O

LH

L

O

C

O

C

L

HHC

O

O

O

HL

L

O

C

O

O