Rockwell Automation 1771-DCM USER MANUAL 1771-DCM - Manual (Page 12)

Selecting Options
Chapter 3
3Ć4
new write block transfer from the local processor until the supervisory
processor has read the previous data from the 1771-DCM.
When you select unprotected data, the local processor updates the
1771-DCM continually, regardless of whether the supervisory processor
has read the data from the 1771-DCM.
Switches 7 and 8 Ć Rack Size
Switch 7 Switch 8 Rack Size
ON ON 1/4
ON OFF 1/2
OFF ON 3/4
OFF OFF Full
When your application requires the transmission of discrete data words,
the 1771-DCM appears to the scanner of the supervisory processor as a
4-, 8-, 12-, or 16-slot remote I/O chassis for the transfer of either 2, 4, 6,
or 8 words respectively. Select the equivalent rack size depending on the
number of words of discrete data you want to write or read. One slot is
equivalent to eight discrete data bits. One module group is equivalent to a
word. A full rack is equivalent to eight data words. The 1771-DCM
inserts one status word in the transfer regardless of the equivalent rack
size you select.
When you set the 1771-DCM for block transfer, the 1771-DCM appears
to the scanner of the supervisory processor as a block transfer module in
the first module group of a four-slot chassis (1/4 rack). You can read and
write up to 64 words including one status word. Slots 1 through 3 are not
used.
The options that you select with Switch Bank 1 are as follows:
Switches 1 through 6 Ć I/O Rack Number
PLCĆ2 Family PLCĆ3 and PLCĆ5/250 PLCĆ5/15 PLCĆ5/25
1 Ć 7 0 thru 37 octal 1 Ć 3 1 Ć 7
Switch Bank 1