Emerson PACSystems Versamax - Page 58

PACSystems VersaMax Genius Network Interface User Manual Section 3
GFK-1535D Jan 2023
Operation 52
Total Amount of Input
and Output Data
Contribution time in ms at each baud rate
153.6 Kb std
153.6 Kb ext
76.8 Kb
38.4 Kb
16 bytes
2.09
2.16
3.83
7.16
32 bytes
3.24
3.31
6.12
11.74
64 bytes
5.52
5.60
10.69
20.89
128 bytes
10.10
10.17
19.85
39.20
256 bytes (fully loaded)
19.25
19.32
38.15
75.80
Procedure for Estimating the GNIU’s Contribution to Genius Bus Scan
Time
1. Find the total number of input bytes and output bytes. (Each
analog channel is 2 bytes. Every eight discrete points are one
byte).
number of input bytes =
number of output bytes =
total bytes =
2. With this total, calculate a scan time contribution using the
formula below that corresponds to the Genius bus baud rate.
The formula for 153.6 Kbaud Standard:
0.943ms + (0.0715 x total bytes) = ms
The formula for 153.6 Kbaud Extended:
1.015ms + (0.0715 x total bytes) = ms
Formula for 76.8 Kbaud:
1.538ms + (0.143 x total bytes) = ms
Formula for 38.4 Kbaud:
2.583ms + (0.286 x total bytes) = ms
Timing Responsiveness
If output in the station is tied to an input in the same station, the output
changes state (or value, in the case of an analog output module) within a
few milliseconds of the new output being sent from the bus controller to
the NIU. (To guarantee that an output changes state, that state must be
present for at least one NIU sweep time or one Genius bus scan time,
whichever is greater.
The input which is tied to the output responds as soon as any load effects
have settled out and input filtering is completed. This may occur as soon
as the NIU’s next I/O scan.