Allen-Bradley SLC 500 DeviceNet, User Manual, Page: 23 / 139

Publication 1747-6.5.5 - August 2000
Before You Begin 1-7
Communicating with Your
SLC 500 Processor
Your processor communicates with the 1747-SDN interface module via
M1 file transfer reads , M0 file transfer writes , and DIO transfers.
Input data, gathered from the network’s devices, is organized within
the 1747-SDN and made available for the processor to “read” from the
M1 file.
The 1747-SDN module does not send data to your processor.
Data transferred between the scanner module and the processor
must be initiated by the processor.
Output data is sent, or “written”,
to the scanner by your processor by placing the data in the M0 file.
This data is organized in the scanner, which in turn passes the data on
to the scanned devices via strobe, poll, change of state, or cyclic
messages.
An M1 file transfer is the transfer of
data from the scanner to the
processor. The scanner makes data
collected from the network’s devices
available for the processor to “read”,
i.e., DeviceNet input data.
An M0 file transfer is the transfer of
data from the SLC 500 processor to
the scanner. The processor “writes"
data to the scanner's memory, i.e.,
DeviceNet output data.
SLC 500 Processor
1747-SDN Scanner
B
A1
C
D
A2
E
E
X
Y
Y
Z
Y
Y
C
D
A2
X
Z
Y
Y
Y
Y
Discrete Input Image
M1/M0 File Transfer Data File
A1
B
E
E
Internal Input
Data Storage
I/O Map
Input from
the devices
Discrete Output Image
M0 Data File
Internal
Output Data
I/O Map
Discrete I/O
Transfer
M0 File
Transfer
(Write)
Discrete I/O
Transfer
M1 File
Transfer
(Read)
Output to
the devices