Agilent Technologies 78581B, Installation And Service Manual

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Theory of Operation
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a. Instrument Identification: Each instrument can be identified as any
SDN bedside monitor, IC, or computer. For bedsides the instrument
identification gives branch number and type of bedside monitor.
b. SDN Communication Error Flags: A variety of SDN system errors are
identified and flagged in the instrument status message. Refer to the
Troubleshooting section for details on the network test and SDN
system troubleshooting.
c. Status Indicators: Three unique status indicators reflect the
instrument’s ability to communicate on the SDN. The three status
indicator bits in the instrument status message are described below.
Each bit can have a value of 0 or 1. In normal operation the status
indicator bits are set to 1.
SDN/Autopoll The normal operating mode is SDN. The ACC’s sync tap indicates to the
instruments that they are in the SDN mode. If operation of the ACC fails
(loses power for example), then one instrument on each branch generates
its own sync taps and talk taps that it sends to itself and to the other
instruments on that branch. Thus, the local communication is maintained.
The locally generated sync tap indicates to the instruments on that branch
that the branch is operating in Autopoll mode.
If the ACC becomes active again, then the branch automatically returns to
the SDN mode.
ONLINE/OFFLINE
The normal operating mode is ONLINE. The ONLINE status indicates that
an instrument has examined itself and is ready and able to operate
reliably on the SDN. At power up an instrument is OFFLINE. When it
successfully completes its own initialization it may put itself in the
ONLINE state.
NETWORK/LOCAL
The normal operating mode is NETWORK. The NETWORK status indicates
that an instrument is synchronized with the system cycle. This is
important because most of the data on the SDN is sent only once each
system cycle, during a specific poll cycle. An instrument must synchronize
with the master poll cycle in order to know when to transmit specific data.
At power up an instrument is in LOCAL mode and starts searching for the
beginning of a system cycle. As soon as a valid system cycle has been
found, the instrument may set itself in NETWORK mode.
SDN Status and Error Conditions
SDN system status and error conditions can be viewed on the IC display,
bedside, and indicated on the ACC via LED status and error code
indicators. A detailed description of the SDN system errors is described in
the SDN troubleshooting section.