Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 43)

Publication 1746-UM005B-EN-P - June 2004
Module Operation and System Considerations 4-5
Processor Update of Analog Data
The analog input and output data is updated by the processor once
during each scan of the user program. The table below shows typical
analog update scan times and the number of input and output bits for
the specified modules.
If an application requires processor updates of the analog data more
frequently than once per scan, use an Immediate Input or an
Immediate Output instruction. An Immediate Input or Output
instruction typically updates 16 bits (or 1 analog channel) in 1
millisecond.
Refer to your programming software’s user manual for more
information.
Monitoring the Input and Output Data
The analog input and output data can be monitored in several
different radices using your programming software. Viewing the radix
as decimal allows the analog input and output data to be viewed as
decimal representations of integer words.
When monitoring in binary radix, data is viewed in two’s complement
representation for negative values. A description of two’s complement
data is available in Appendix B.
Typical Time for Analog Data Updates to the Processor’s Input and Output Image
Once per processor scan
(Automatic)
10 milliseconds for typical
1K program
Using immediate Input or Output
Instruction
1 millisecond per analog
channel
Number of Input and Output Bits Representing Analog Data
Description Input Bits Output Bits
NI4 64 -
NI4OI and NIO4V
(2 input and 2 Output
channels)
32 32
NO4I and NO4V - 64