Rockwell Automation 1771-SDN DeviceNet Scanner Module Installation Instructions - Manual (Page 21)

Publication 1771-IN014B-EN-P - September 2001
DeviceNet Scanner Module Catalog Number 1771-SDN/C 21
Use BTR to Upload Input Data from the Scanner
The PLC-5 uploads input data from the scanner using block transfer
read instructions over the 1771 backplane. The scanner interprets
BTRs of length 1 through 50 and 62 words as being from the first
block of the scanner input table. The scanner module can update a
maximum of 357 input words by internally linking together six
different sized block transfers. See the table below.
Each individual block transfer is independent, but always retrieves the
same input bytes from the scanner’s input data table. The types of
information that a PLC-5 program will upload from the scanner via the
BTR are the:
•
Device Input Data Table (6 blocks, 62 through 57 words)
•
Device Failure Table (1 block, 52 words)
•
Device Active Table (1 block, 51 words)
When the scanner receives a BTR, it automatically knows which block
of data is desired by the size specified.
You may upload portions of the scanner input table rather than the
entire table, to support higher-speed operations. The scanner will
interpret any BTR of length 1 through 50 with the words 0 thru 49 of
block 62 of the scanner input table. BTRs of sizes 57 through 61
represent full blocks of the table. A BTR of 52 words contains the
Device Failure Table. Sizes 53 through 56 are reserved. Size 64 is used
for Explicit Message Program Control. For more details on Explicit
Message Program Control, refer to page 26.
Block
Transfer Size
Accessed
Scanner
Input Block
Scanner Input Data Table
62 words Block 62
Word 0 – Module Status Register Word
Words 1–61
61 words Block 61 Words 62–122
60 words Block 60 Words 123–182
59 words Block 59 Words 183–241
58 words Block 58 Words 242–299
57 words Block 57 Words 300–356
52 words Block 52 Device Failure Table
51 words Block 51 Device Active Table
1-50 words Block 1-50 Words 0–49
DeviceNet Messages