Rockwell Automation 1757-SWKIT5100 ProcessLogix R510.0 Installation and Upgrade Guide - Manual (Page 265)

Publication 1757-IN510A-EN-P - October 2003
Performance and Capacity Specifications 11-25
I/O Module Publication Periods
Special Considerations The following paragraphs describe known problems and limitations
found in this release.
Device Control May Generate Nuisance Alarms
Er r or Indication: DevCtl generates a Command Disagree alarm that
returns to normal at the same time.
Descr iption: Problem occurs when a DevCtl block is commanded to
different states very quickly, i.e. as soon as the DevCtl PV feedback
reaches the first OP state commanded, then a different OP command
is provided. When this different state command after a previous
command happens along with a) the internal DevCtl Command
Disagree timer expiring, and b) PV changing to the previous
commanded state during the same execution cycle of the DevCtl, then
the nuisance alarm will be generated.
Recover y: Nuisance Command Disagree alarm can safely be ignored.
Table 11.W I/O Module Publication Period Specifications
Input Module types Publication Period
Typical Input Module
Includes 1757/1756, 1797-FLEX Ex and 1794-FLEX I/O input modules, and CN2FFs with exceptions
noted below 25 ms
High Density / Non-Isolated Analog Input Module (1756-IF16) 250 ms
RTD Module (1756-IR6I) 50 ms
Thermocouple Module (1756-IT6I) 50 ms
Serial Interface Module (TC-MUX021) 250 ms
Digital Input Module used by 5 ms CEE (local only) 1 ms
For CMs which contain associated input channels, it is recommended that the CM execution period should be set to at least double the
input module sampling period.
Output Module Type Publication Period
Typical Output Module
1757/1756,1797-FLEX EX, and 1794-FLEX I/O Output Modules 50 ms
Input/Output Module Type Publication Period
PFB Module (SST-PFB-CLX)
Note: Update rate is configurable on the PBIM block. Default = 25 ms
Minimum =
12.5 ms (remote chassis)
5 ms (local chassis)
Maximum = 50 ms