Agilent Technologies 78581B, Installation And Service Manual

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Agilent CareNet Controller (ACC), Model 78581B
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Agilent CareNet Controller (ACC), Model 78581B
The Agilent CareNet Controller (ACC), model 78581B, is the active node—
in essence the heart—of the Serial Distribution Network (SDN). The
primary functions of the ACC are to provide the physical system
communications link to the instruments connected to the SDN, to establish
the SDN data polling cycles, and to control the data flow, timing,
synchronization, and distribution throughout the system.
The ACC functions in conjunction with the SDN Interface Circuitry located
within each instrument connected to the SDN, and with the system
distribution cables (branch cables), local distribution cables, and the
associated wallbox hardware, connectors and receptacles. A typical SDN
system configuration is illustrated in Figure 1-2 on page 1-3.
Once each poll cycle, data from each instrument is transmitted over the
branch cables to the ACC. All this data are received in sequence,
synchronized, and controlled by the ACC, then transmitted (broadcast)
simultaneously to all of the instruments connected to the SDN during each
32-millisecond poll cycle. The data sent over the SDN bus is received for
use by each instrument via the SDN interface circuitry residing in each
instrument. The ACC cannot store, restrict, or allocate specific
distribution of SDN data.
The ACC controls the data communication sequence during the 32-
millisecond poll cycle by issuing a variety of system messages that
originate in the ACC. A complete description of system messages,
instrument messages, the SDN data communicating sequence and SDN bus
direction control is described in the SDN system theory of operation
section of this manual.
Additionally, the ACC performs some basic fault detection isolation to
ensure reliability of SDN system communications. Also included in the
ACC are resident self-diagnostic routines for fault detection,
troubleshooting, and servicing of the ACC.
The ACC consists of a metal chassis with cover, a Power Supply Assembly,
a Terminal Interconnect PC board, and a Control/Driver PC board. The
model 78581B Agilent CareNet Controller is illustrated on in Figure 1-3 on
page 1-5.
The Control/Driver PC board contains all the electronic circuitry required
to control the data flow, timing, and distribution of SDN data throughout
the system.
The Terminal Interconnect PC board contains the RJ-45 connection to
connect the branch cables to the ACC, and the signal feed-through ribbon
cables to the Control/Driver PC board.
The Power Supply assembly contains the power ON/OFF indicator, and a
5-volt linear DC voltage supply used to power the circuitry on the Control/