USER MANUAL 1771-DCM User Manual

Overview of Direct
Communication Module
Chapter 2
23
Baud Rate/Distance Select the communication rate and distance to the supervisory proces 
sor as either 57.6K baud to a distance of 10,000 feet, or 1 15.2K baud
to a distance of 5,000 feet.
T ransfer Method Select block transfer or discrete data transfer between the 1771DCM
and the supervisory processor .
Rack Size When using discrete data transfer , select the number of slots that de 
termines how the 1771DCM appears to the scanner of the superviso 
ry processor (the size of the I/O chassis simulated by the 1771DCM).
This also determines the number of words transferred.
Protected Data Select protected data to prevent block transfers from the local proces 
sor until the supervisory processor has received the previous block
transfer.
I/O Rack Address Designate the I/O rack number, the number of the first module group
of the I/O chassis simulated by the 1771DCM, and whether it has the
highest starting module group address of two or more chassis as

signed to the same rack address.
These options are described in Chapter 3.
You can use the 1771-DCM in a variety of applications where the transfer
of data table values is required. For example, consider using it to:
Call messages stored in the data table of the supervisory processor and
outputted through an ASCII I/O module (cat. no. 1771-DA) or BASIC
module (cat. no. 1771-DB)
Download recipe data table values from supervisory to local
processor(s) where you want local processor(s) to execute different
versions of the same program
Download commands from the supervisory processor to execute
different sections of a ladder diagram program at the local processor
Use the 1771-DCM with any Allen-Bradley programmable controller that
uses block transfer and the 1771 I/O structure.
Reserve an I/O slot for this module by placing keying bands on the
backplane connector. Position keying bands between the following
numbers labeled on the backplane adjacent to the upper backplane
connector. The keying bands mate with corresponding slots in the module
connector:
Between 2 and 4
Between 16 and 18
Example Applications
Compatible Processors
Keying