Rockwell Automation 1771-VHSC , D17716.5.74 Very High S - Manual (Page 47)

Chapter
5
Module Status and Input Data
In this chapter you will read about:
•
reading data from your module
•
module read block transfer format
Block transfer read (BTR) programming moves status and data from
the input module to the processor’s data table (Table 5.A). The
processor user program initiates the request to transfer data from the
module to the processor.
The module transfers up to 26 words to the processor’s data table
file. The words contain module status and input data from each
channel. When a BTR of length 0 is programmed, the module
returns 18 words.
Important: Words 19 through 26 are optional, and are accessed
only by programming a BTR length greater than 18
words. Words 19 through 26 are only valid if in
period/rate or continuous/rate modes. In any other
mode words 19 through 26 are zero.
Table 5.A
BTR Word Assignments for the VHSC Module (1771ĆVHSC)
(Octal Bit) 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
Decimal Bit 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
1 Diagnostics (always in BCD) New Data Not Used PU*
2 Not used
Gate/Reset input
state
Status of outputs
3 Counter 0 MSD (0Ć999)
4 Counter 0 LSD (0Ć999)
5 Counter 1 MSD (0Ć999)
6 Counter 1 LSD (0Ć999)
7 Counter 2 MSD (0Ć999)
8 Counter 2 LSD (0Ć999)
9 Counter 3 MSD (0Ć999)
10 Counter 3 LSD (0Ć999)
11
Counter 0 Store count values MSD (range 0Ć999) in encoder/counter mode; or frequency
value MSD (range 0Ć500) in rate measurement or period/rate mode
12 Counter 0 Store count values LSD (range 0Ć999)
Chapter Objectives
Reading Data from the
Module
Block Transfer Read for
the 1771ĆVHSC Module