Micro-Aide LDM-1 plug-in, Руководство пользователя

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LDM User Manual
34
ously active state. Refer to the section entitled “Permanently Asserting the
RTS” on page 15 for details.
M
ULTI
-D
ROP
Multi-drop networks require slave LDM-1s to be connected only to DTEs
that support hardware handshaking. The MICRO-AIDE LCU supports this
requirement. However, the hardware handshaking option must be enabled in
the Coastcom PSDM. The user should consult Coastcom for information on
how a PSDM is enabled for hardware handshaking.
Another consideration in multi-drop networks concerns the number of
LDM-1s that can be placed in one branch of the network. No more than
seven slave LDM-1s can communicate with a master LDM-1.
RS-232 C
ABLES
Each LDM-1 is equipped with a standard DB-25 female connector. The con-
nector is wired in accordance with DCE standards. The pin assignments for
the connector are illustrated in Figure 7 on page 31. The following list pro-
vides the user with additional information concerning cable types.
LCU
TO
LDM-1
The LCU to LDM-1 cable is a simple one-to-one cable with DB-25 male con-
nectors at each end. A one-to-one cable can be purchased at any computer
supply store. It can also be easily assembled using 25-conductor, flat-ribbon
cable and connectors.
PSDM
TO
LDM-1
The PSDM must first be configured for hardware handshaking. The correct
setting involves having the RTS signal track the state of the CD signal. A stan-
dard null modem cable can then be used to interconnect the PSDM and
LDM-1.
ADU
TO
LDM-1
The ADU to LDM-1 cable must be assembled in such a way that the LDM-1
is given a constantly asserted RTS signal. The best way to achieve this is to
wire pins 4 and 6 together at the LDM-1 end. This allows the RTS to be con-