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3
Main
Sub-assemblies
Printed Circuit
Assembly
Multiplexer-to-Panel
Cables
Functional Description
The HP 27140A Asynchronous 6-Channel Multiplexer with Modem
Control is, in most cases, the primary RS-232-C interface for your com-
puter. Your control of this MUX may be through a high level language,
such as C or FORTRAN, a "turn-key" application program, or some other
type
of program which uses the computer operating system to control the
interface. Since the user contact with the MUX is at such a high
leve~
the
functional description below dermes the interface organization in terms of
a few large functional blocks. This manual does not contain a component
level description of the operation of the interface.
Three major sub-assemblies constitute the 27140A: the Multiplexer PCA,
the 6-port RS-232-C J unction
Pane~
and the Multiplexer-to-Panel cables.
Figure 3-1 shows these sub-assemblies. See "Equipment Supplied" in
Chapter 1 for sub-assembly part numbers.
A Channel Input/Output (CIO) PCA fits into a CIO backplane, gets its
power from the backplane, and receives data from the host computer and
peripheral devices. The multiplexer PCAconverts signals and data from
the CIO backplane protocol to the RS-232-C protocol used by
peripherals. Conversely, the MUX also converts data from up to six RS-
232-C peripherals to the CIO protocol.
These cables are used to
carry
signals to and from the RS-232-C Junction
Panel in a single, manageable package. The cable contains six sets of wire.
Each set is dedicated to one of the communication channels. The braided
shield just under the cable outer jacket connects the safety ground on the
card to the safety ground on the panel.
Depending on how your computer is installed, the standard MUX-to-
Panel cable may go to a RS-232-C Junction Panel that is on the inside or
the outside of the computer main cabinet. The cable 62-pin male connec-
tor plugs into the large RS-232-C Junction Panel receptacle. If the panel
must be located farther from the computer, an extension cable is available
as an option.
Functional Description 3-1
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