Emerson PACSystems Versamax - Genius Bus Scan Time

PACSystems VersaMax Genius Network Interface User Manual Section 3
GFK-1535D Jan 2023
Operation 51
%AQ tables. Each discrete output module receives one byte of data for
every eight points. Each analog output module receives two bytes (one
word) for each analog channel
Output Defaults
During its first I/O scan after power-up, the GNIU sets each of its outputs
to its configured default value (unless that output had been previously
forced). Outputs that had been previously forced remain set to their
forced values.
When the first error-free outputs message from a bus controller arrives,
the NIU sets its I/O Enabled LED to green and updates each output
module with the new output values (unless the output is currently
forced).
When no redundancy features are configured for the GNIU, if the NIU
loses contact with its host for three successive Genius bus scans, the NIU
sets its I/O Enabled LED to amber and sets each of its outputs to its
configured default value (unless the output is currently forced).
When redundancy features are configured (such as “Hot Standby”,
“Duplex”, “GMR”, “BSM Controller”, or “BSM present”), the NIU operates as
described in Section 6: Redundancy.
3.4 Genius Bus Scan Time
The Genius bus scan time depends on the number of devices on the bus
as well as the amount of I/O traffic on the bus. The bus scan time may
vary from 3- 400ms, but 20-30ms is typical. It cannot be less than 3ms.
The Genius bus scan time contribution for the NIU depends on its I/O
data usage. The table below shows the scan time contribution, at each
baud rate, for stations with a total of 16, 32, 64, 128, and 256 bytes, when
the NIU receives outputs from only one bus controller at a time.
To find the exact scan time contribution for the NIU, follow the procedure
on the next page.