Datasheet

LTC1544

Mode Selection

The interface protocol is selected using the mode select

pins M0, M1 and M2 (see the Mode Selection table).

For example, if the port is configured as a V.35 interface,

the mode selection pins should be M2 = 1, M1 = 0, M0 = 0.

For the control signals, the drivers and receivers will

operate in V.28 (RS232) electrical mode. For the clock and

data signals, the drivers and receivers will operate in V.35

electrical mode. The DCE/DTE pin will configure the port

for DCE mode when high, and DTE when low.

The interface protocol may be selected simply by plug-

ging the appropriate interface cable into the connector.

The mode pins are routed to the connector and are left

unconnected (1) or wired to ground (0) in the cable as

shown in Figure 10.

The internal pull-up current sources will ensure a binary 1

when a pin is left unconnected and that the LTC1543/

LTC1544 and the LTC1344A enter the no-cable mode

when the cable is removed. In the no-cable mode the

LTC1543/LTC1544 supply current drops to less than

200µA and all LTC1543/LTC1544 driver outputs and

LTC1344A resistive terminations are forced into a high

impedance state.

The mode selection may also be accomplished by using

jumpers to connect the mode pins to ground or V

CABLE

1544 F10

LTC1543

LTC1544

CONNECTOR

M2 M1

LTC1344A

LATCH

M0 (DATA)

23 24 1

(DATA)

DCE/DTE

(DATA)

DCE/

DTE

Figure 10: Single Port DCE V.35 Mode Selection in the Cable

APPLICATIONS INFORMATION

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