Allen-Bradley SLC 500 DeviceNet, User Manual, Page: 25 / 139

Publication 1747-6.5.5 - August 2000
Before You Begin 1-9
The Scanlist Table (SLT)
The SLT supports I/O updating for each of your devices on the
network. It also makes it possible for your 1747-SDN module to make
device data available to your SLC processor. The SLT tells your
1747-SDN module:
•
which device node addresses to scan
•
how to scan each device (strobe, poll, change of state, cyclic or
any valid combination)
•
how often to scan your devices
•
exactly where in each device’s total data to find the desired data
•
the size of the input data/output data
•
exactly where to map the input or output data for your
processor to read or write
•
how your processor reads each device’s input data (M1/M0 file
or DIO)
RSNetWorx Software as a
Configuration Tool RSNetWorx for DeviceNet software is used to configure the 1747-SDN
module’s data tables. This software tool connects to the 1747-SDN
module over the DeviceNet network via a PC RS-232 interface
(1770-KFD module) or PC Card (1784-PCD, -PCID, or -PCIDS).
User
Configured
Tables Data In This Table RSNetWorx
Configuration Screen
SCT • basic operation parameters
• I/O communications data
(enable/disable)
• interscan delay
• background poll ratio
1747-SDN Module
Configuration
SLT • device-specific identification
data
Scanlist Editor (SLE)
• data transfer method
• transmit/receive data size Edit Device I/O Parameters
• input and output data source
and destination locations
These values can be configured
automatically through the
AutoMap function or manually
through the Data Table Map.
Interscan delay is the time between
I/O scans (polled and strobed). It is
the time the 1747-SDN module will
wait between the last poll message
request and the start of the next scan
cycle.
Background poll ratio sets the
frequency of poll messages to a
device in relation to the number of
I/O scans. For example, if the ratio
is set at 10, that device will be
polled once every 10 scans.
TIP
RSNetWorx for DeviceNet software can also
communicate with the 1747-SDN module via an
Ethernet or Data Highway Plus network. See
chapter 5.