14
LTC1543
sn1534 1543fas
DTE vs DCE Operation
The DCE/DTE pin acts as an enable for Driver 3/Receiver
1 in the LTC1543, and Driver 3/Receiver 1 and Driver 4/
Receiver 4 in the LTC1544. The INVERT pin in the LTC1544
allows the Driver 4/Receiver 4 enable to be high or low true
polarity.
The LTC1543/LTC1544 can be configured for either DTE
or DCE operation in one of two ways: a dedicated DTE or
DCE port with a connector of appropriate gender or a port
with one connector that can be configured for DTE or DCE
operation by rerouting the signals to the LTC1543/LTC1544
using a dedicated DTE cable or dedicated DCE cable.
A dedicated DTE port using a DB-25 male connector is
shown in Figure 23. The interface mode is selected by logic
outputs from the controller or from jumpers to either V
CC
or GND on the mode select pins. A dedicated DCE port
using a DB-25 female connector is shown in Figure 24.
A port with one DB-25 connector, but can be configured
for either DTE or DCE operation is shown in Figure 25. The
configuration requires separate cables for proper signal
routing in DTE or DCE operation. For example, in DTE
mode, the TXD signal is routed to Pins 2 and 14 via Driver
1 in the LTC1543. In DCE mode, Driver 1 now routes the
RXD signal to Pins 2 and 14.
Multiprotocol Interface with RL, LL, TM and a DB-25
Connector
If the RL, LL and TM signals are implemented, there are not
enough drivers and receivers available in the LTC1543/
LTC1544. In Figure 26, the required control signals are
handled by the LTC1544 but the clock/data signals use the
APPLICATIO S I FOR ATIO
WUUU
LTC1343. The LTC1343 has an additional single-ended
driver/receiver pair that can handle two more optional
control signals such as TM and LL.
Cable-Selectable Multiprotocol Interface
A cable-selectable multiprotocol DTE/DCE interface is
shown in Figure 27. The select lines M0, M1 and DCE/DTE
are brought out to the connector. The mode is selected by
the cable by wiring M0 (connector Pin 18) and M1 (con-
nector Pin 21) and DCE/DTE (connector Pin 25) to ground
(connector Pin 7) or letting them float. If M0, M1 or DCE/
DTE is floating, internal pull-up current sources will pull
the signals to V
CC
. The select bit M2 is hard wired to V
CC
.
When the cable is pulled out, the interface will go into the
no-cable mode.
Compliance Testing
A European standard EN 45001 test report is available for
the LTC1543/LTC1544/LTC1344A chipset. A copy of the
test report is available from LTC or TUV Telecom Services
Inc. (formerly Detecon Inc.)
The title of the report is:
Test Report No. NET2/102201/97.
The address of TUV Telecom Services Inc. is:
TUV Telecom Services Inc.
Type Approval Division
1775 Old Highway 8, Ste 107
St. Paul, MN 55112 USA
Tel. +1 (612) 639-0775
Fax. +1 (612) 639-0873
