Rockwell Automation 20-COMM-R Remote I/O Adapter - Manual (Page 40)

4-4 Using Discrete and Block Transfer I/O
20-COMM-R Remote I/O Adapter User Manual
Publication 20COMM-UM004D-EN-P
Discrete I/O Image The Discrete I/O image is either a 1/4 rack or 1/2 rack. Use Configuration
DIP Switch SW4 to select 1/4 rack or 1/2 rack or, if the hardware switches
have been disabled, adapter Parameter 27 - [Rack Size]. The I/O that is
transmitted depends on the size of the rack.
Figure 4.1 shows a 1/4 rack I/O
image, and Figure 4.2 shows a 1/2 rack I/O image.
Data in the Discrete I/O image is transferred between the controller and
Remote I/O adapter every scan.
Block Transfer Control/Status Word
Word 0 in the Discrete I/O image is always the 16-bit Block Transfer
Control/Status word. The ‘Block Transfer Control’ word is used for
handshaking between the scanner and adapter. Do not change this word.
The ‘Block Transfer Status’ word is used to determine when you can write
and read Block Transfers for Explicit Messages. The section
Executing
Block Transfers for Explicit Messages on page 5-5 explains the bits in this
word and how to use them. Block Transfer I/O does not use the Block
Transfer Status word.
Logic Command/Logic Status in Discrete I/O Image
Word 1 in the Discrete I/O image is always the Logic Command/Logic
Status word. The ‘Logic Command’ word is a 16-bit word that is used to
control the drive (for example, start, stop, change direction). The ‘Logic
Status’ word provides details about how the drive is operating. PowerFlex
750-Series drives have a 32-bit Logic Command/Status word—but when
using the 20-COMM-R adapter only the first 16 bits can be used.
This manual contains the bit definitions for most compatible products
available at the time of publication in
Appendix D , Logic Command/Status
Words . For other products, see their documentation.
Reference/Feedback in Discrete I/O Image
If the adapter is configured for 1/2 rack ( Figure 4.2 ), word 2 and word 3 in
the discrete I/O image are reserved for Reference/Feedback.
LSW = Least Significant Word (bits 0…15)
MSW = Most Significant Word (bits 16…31)
The Reference is produced by the controller and consumed by the adapter.
The Feedback is produced by the adapter and consumed by the controller.
The size of the Reference/Feedback is determined by the drive and can be
displayed using adapter Parameter 07 - [Ref/Fdbk Size].
Word 16 -bit value 32-bit value
2
3
Reference
Not Used
Feedback
0
Reference (LSW)
Reference (MSW)
Feedback (LSW)
Feedback (MSW)