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

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LDM User Manual
8
LDM-1 B
ASICS
The LDM-1 can be thought of as a device that extends the distance that
RS-232 serial data can be transmitted and received. It does so over four-wire
(i.e., two pair) private line networks. It includes a standard DB-25 female con-
nector that allows for direct connection to any DTE device. The LDM-1 is
configured as a DCE device. Refer to Figure 7 on page 31.
Regardless of the network configuration (refer to section entitled “Network
Types” on page 9) at least two modems must be used. The master modem
broadcasts to one or more slave modems. Each slave modem listens to the
data on its receive channel and passes that data to its DTE device. Under con-
trol of its DTE device only one of the slave modems is allowed to respond at
a time to the master modem’s message. The slave modem sends data via its
transmit channel.
The basic transmit and receive methodology employed is summarized by the
following rules.
• Only one master modem can be employed per network.
• The master modem broadcasts simultaneously to every slave modem.
• Only one slave modem can respond to the master modem at a time. It can
only transmit data to the master modem (i.e., not to another slave modem).
• The slave DTE device, via its application, controls the response of each
slave modem.
• Hardware flow control must be enabled within each DTE device. Specifi-
cally, the DTE device must not attempt to send data until its modem has
asserted its Clear to Send (CTS) signal.
• If only two modems are used, as is the case in a point-to-point network, the
RTS signal of each modem can be permanently asserted. Refer to the section
entitled “Permanently Asserting the RTS” on page 15.
N
OTE
: The LDM-1 (master or slave) will only transmit data when its
Request to Send (RTS) signal is asserted and the LDM-1 has in response
asserted its CTS signal.