Multitech MMH900 User Manual page 14

Chapter 1 - Introduction & Description
channel devices and the composite link. The async devices are
connected to CHANNEL 1 through CHANNEL 4 connectors on the back
panel of the MultiMux MMH904 with an RS232 cable. The MultiMux
MMH908 has four additional channel connectors for connecting up to
eight devices.
A number of internal and external composite link devices can be used to
connect the MultiMux to the PDN. The MMH900 series has an internal
28,800 bps composite link modem or an internal 56,000 bps DSU. The
modem is connected to the PDN through the INTERNAL COMPOSITE
LINK LEASED MODEM connector on the back panel of the MultiMux.
The internal DSU is connected to a DDS or dedicated network through
the COMPOSITE LINK DIGITAL DSU connector on the back panel.
The supervisory console is connected to the MultiMux through the
COMMAND PORT connector on the back panel. The supervisory
console connection is also an RS232 connection. This completes a
typical hardware setup for a MultiMux. Now the MultiMux has to be
configured to talk to the channel devices and communicate over the
composite link.
Configuration of a MultiMux is accomplished through a combination of
setting DIP switches behind the front panel and software commands
entered through the supervisory console. The DIP switches determine
whether the MultiMux is a four or eight channel multiplexer, whether the
composite link device is an internal modem or DSU or an external
device, whether or not the command modem will accept remote access,
etc. The DIP switches control the hardware setup and the operating
setup is controlled through software commands. The software
commands are entered at a terminal connected to the COMMAND
PORT which are transferred to either the command processor or
command modem in the MultiMux. The software commands are AT
commands that configure the channel devices to communicate with the
MultiMux and configure the composite link device to communicate with
the PDN. To configure a channel device, the correct channel speed has
to be established, number of data and stop bits in a word determined,
the type of flow control and whether or not it is used and whether or not
pacing is active. These are just some of the AT commands that are used
to configure and display the status of the channel devices.
When the MultiMux MMH900 series is powered up, the command
processor transfers the stored configuration of the channel devices to
the data processor. The data processor takes the configuration
information and configures each channel for its particular conditions.
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