Rockwell Automation 1395 Multi-Comm Hardware/Software - Manual (Page 39)

Chapter 3
Configuration & Interfacing
3–28
RIO Redundant Mode
The RIO redundant mode is a special mode that allows the Drive to be
connected to the RIO channel of two separate PLC Controllers. A
parameter in the Drive specifies which PLC Controller has control of the
Drive. Output image table data from the non-controlling PLC is discarded.
Figure 3–19 shows a typical redundant mode configuration. The redundant
RIO mode is only available when the following three conditions are met:
1. Both channels of the MCA board are configured for RIO protocol.
2. The DIP switch for channel A is set for redundant mode.
3. Both channels are the same size. For example, both must be configured
for full rack, 3/4 rack or 1/2 rack.
The redundant mode operates as follows:
Data from the output image table of each PLC Controller is transferred to
the MCA board by the respective PLC Controllers.
The RIO Redundant Channel Number parameter (Par. #538) determines
which PLC Controller’s outputs will be made available to the Drive via
parameters 300 through 306. Indication of which channel has control is
provided by the DCSTATUS word (Bit 15 Decimal, Bit 17 Octal) in BT
Status Flags.
Each PLC Controller input image table receives data from the Drive via
parameters 350 though 356.
Block transfer messages from both drives are processed as normal. Only
output image table data is discarded.