9
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
CC
.
NC
NC
CABLE
1544 F10
11
12
13
14
LTC1543
LTC1544
CONNECTOR
14
13
12
11
22
21
M2 M1
LTC1344A
LATCH
M0 (DATA)
23 24 1
(DATA)
M0
M1
M2
DCE/DTE
DCE/DTE
M2
M1
M0
(DATA)
DCE/
DTE
Figure 10: Single Port DCE V.35 Mode Selection in the Cable
APPLICATIONS INFORMATION
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