Rockwell Automation 1771-DCM USER MANUAL 1771-DCM User Manual
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Selecting Options
Chapter 3
3Ć3
Switch 3 Ć Last Rack
ON (Closed) Not Last Rack
OFF (Open) Last Rack
If the 1771-DCM is assigned the same I/O rack number as other I/O
chassis, designate whether this I/O chassis is the last chassis (has the
highest starting module group number) of those assigned the same rack
number. (Refer to I/O Rack Number below.)
Switch 4 Ć Transfer Method
ON (Closed) for Block Transfer
OFF (Open) for Discrete Data Transfer
Choose either discrete data transfer or block transfer between the
supervisory processor and 1771-DCM. With discrete transfer, the rack
size you select determines the number of words transferred as either 2, 4,
6, or 8 words including a status word. Data is transferred between the
1771-DCM and the supervisory processor as serial remote I/O data for
each slot of the simulated I/O chassis. The supervisory processor updates
the 1771-DCM as if it were an I/O chassis on a remote I/O link.
With block transfer, you can transfer up to 64 words including a status
word. The 1771-DCM appears to the supervisory processor as a remote
1/4 rack. Data is transferred between the first I/O slot simulated by the
1771-DCM and the supervisory processor when the supervisory
processor’s ladder program executes block transfers.
Communication between the 1771-DCM and local processor is always
block transfer regardless of the mode of communication between
1771-DCM and supervisory processor.
Switch 5 Ć Not Used
Switch 6 Ć Protected Data
ON (Closed) for Unprotected Data
OFF (Open) for Protected Data
This option maintains data integrity and maintains the order of data blocks
sent from the local processor to the supervisory processor only when you
select block transfer. The 1771-DCM does not recognize the start of a