Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual - Manual (Page 134)

Publication 1747-UM655B-EN-P - June 2007
134 Data Organization
Upload Input Data from the
Module to the SLC
Processor The SLC 500 processor reads input data from the module by using two
methods.
•
Input image table
•
M1 file transfer
Input Image Table
The input image table is a 32-word table for the module slot that is
updated by the processor with each program scan. The first word
(word 0) is reserved for the module status register. The remaining 31
words can be used to transfer DeviceNet input data to the SLC input
image table. The addressing format is:
I:S.w/b
Where S = slot
w = word (0…31)
b = bit (0…15)
Module Status Register
The module status register is located at word 0 in the input image area
for the slot. Bits 0…5 echo back to the processor, the current state of
bits 0…5 of the module command register. The echoes verify that the
commands were executed. The module sets the remaining bits when
it detects a problem. The bits latch in the ON state until the problem
clears. Bits 6 and 8 indicate that you should read the device failure
table for more specific information about which devices failed.
You can use bit 6 to keep the communication port in the Idle mode
until the bit clears. When the bit clears, this indicates that all devices
in the scanner’s scanlist are up and available. When the devices are
available, you can put the port in Run mode. If a device failure is
detected, you can put the communication into the Idle mode, so that
all output devices go to a safe state.
The SLC program can monitor the bits in the module status register
and set the appropriate bits of the module command register to
automatically control the operating mode of the module should a
device failure occur.