Rockwell Automation 1769-OF2 Compact I/O Analog Modules - Manual (Page 58)

Publication 1769-UM002B-EN-P - July 2005
3-8 Module Data, Status, and Channel Configuration for the Input Modules
Module Update Time and Scanning Process
The module update time is defined as the time required for the module to
sample and convert the input signals of all enabled input channels and provide
the resulting data values to the processor. Module update time can be
calculated by adding the sum of all enabled channel times. Channel times
include channel scan time, channel switching time, and reconfiguration time.
The module sequentially samples the channels in a continuous loop.
Figure 3.3 Sequential Sampling
Table 3.5 shows the channel update times. The fastest module update time
occurs when only one channel is enabled with a 500 Hz filter (4 ms). If more
than one channel is enabled, the update time is faster if both channels have the
same configuration. See the first example on page 3-9. The slowest module
update time occurs when all four channels are enabled with different
configurations. See the second example on page 3-9.
Channel Switching and Reconfiguration Times
The table below provides the channel switching and reconfiguration times for
a channel.
Channel 0 Disabled Channel 1 Disabled Channel 2 Disabled Channel 3 Disabled
Sample
Channel 0
Sample
Channel 1
Sample
Channel 2
Sample
Channel 3 Enabled Enabled Enabled Enabled
Table 3.5 Channel Update Time
Filter Frequency Channel Update Time
50 Hz 22 ms
60 Hz 19 ms
250 Hz 6 ms
500 Hz 4 ms
Table 3.6 Channel Switching and Reconfiguration Times
Description Duration
50 Hz 60 Hz 250 Hz 500 Hz
Channel Switching
Time The time it takes the module to switch from one channel to
another. 46 ms 39 ms 14 ms 10 ms
Channel-to-Channel
Reconfiguration Time The time it takes the module to change its configuration settings
for a difference in configuration between one channel and another. 116 ms 96 ms 20 ms 8 ms