Black Box IC108A Guía de usuario descargar pdf (Pagina 94)

Advant

Smart Device (HART

) Interface User’s Guide

Chapter 4 Runtime Operation

4-4 3BUR 001 085R0001 REV A

Redundancy

No provisions are made to directly support any smart device vendors specific redundancy

scheme. The redundant port can be any other port in the Advant Controller CPU. When the

Advant smart device interface loses communications with the primary port and the backup port

is “communicating”, then a swap to the backup port is performed. Loss of communications is

determined by a predefined set of error conditions. The MVI automatically performs

communications testing to the configured smart devices on a given port, the application need

only check the status word in the MOD300 database for the current state of the backup port.

Error Conditions

The following is a list of error conditions which will cause the Advant smart device Interface to

attempt a swap to the backup communications port.

• Link down,

• Board Unavailable.

4.2.2 Start-up

During start-up from SSE the Advant Smart Device (Hart) Interface examines the MOD300

database to see if it has been defined. If it has, it creates any additional buffers it might need then

starts the scanner, transmitter, receiver, momentary output, request output, backup monitor and

diagnostic input tasks. It also will signal CCF that it has completed its start-up and one full scan

of data. If it is not defined it will signal CCF that it is complete and does not exist.

4.2.2.1 Coordination Signals

The Serial Interface will not allow commands to be processed by it until it has sent

configuration data to the MVI board. So the interface must check the MOD300 database to

verify the status of the port before attempting any outputs. CCF must also wait, but it waits for

the smart device interface to complete one full scan and update all the data tables before

continuing processing. If the MVI can not be configured or a scan completed then CCF is

signalled to continue but with bad data quality for all smart device points. The time before the

bad data quality is set is a user configurable function (Good Data Wait).

4.2.2.2 Scanner Task

The scanner processes each smart device on every port and requests the configured data. The

scanner runs at a user configurable base rate and requests data at the segment’s configured scan

rate, a multiple of the base rate. The request goes to the end of the transmitter output queue for

output to the device. If the segment is a Scan Complete Acknowledge it is processed in one of

two ways. If the segment’s scan rate is zero then the command is sent after the READ command

with the longest scan rate, or if it is a non-zero value then the command will go out at that given

scan rate like a READ command. Note: if there are no read commands, which must have a scan

rate, then the SCA must have a scan rate.

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Black Box IC108A Guía de usuario Pagina 94