Datasheet

11
LTC2844
sn2844 2844fs
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 LTC2846/
LTC2844 enter the no-cable mode when the cable is
removed. In the no-cable mode the LTC2846/LTC2844
supply current drops to less than 900µA and all driver
outputs 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
IN
.
Figure 10. Single Port DCE V.35 Mode Selection in the Cable
APPLICATIONS INFORMATION
WUU
U
NC
NC
CABLE
2844 F10
15
16
18
19
LTC2846
LTC2844
CONNECTOR
14
13
12
11
(DATA)
M0
M1
M2
DCE/DTE
DCE/DTE
M2
M1
M0
(DATA)