Rockwell Automation 1771-IXE/D Thermocouple/Millivolt Input Module User Manual - Manual (Page 31)

4–3 Module Configuration
Publication 1771Ć6.5.130 Ć May 1999
You must indicate what format will be used to read data from your
module. Typically, BCD is selected with PLC–2 processors, and
binary (also referred to as integer or decimal) is selected with PLC–3
and PLC–5 processors. See Table 4.B and Appendix C for details on
Data Format.
Table 4.B Selecting Format for Reading Data
Decimal Bit 10
Octal Bit 12
Decimal Bit 9
Octal Bit 11
Data Format
0 0 BCD - binary coded decimal
0 1 2'scomplement binary
1 0 Signed magnitude binary
1 1 Same assigned magnitude binary
The real time sampling (RTS) mode of operation provides data from
a fixed time period for use by the processor. RTS is invaluable for
time based functions (such as PID and totalization) in the PLC. It
allows accurate time based calculations in local or remote I/O racks.
In the RTS mode the module scans and updates its inputs at a user
defined time interval (
∆
T) instead of the default interval. The
module ignores block transfer read (BTR) requests for data until the
sample time period elapses. The BTR of a particular data set
occurs only once at the end of the sample period and subsequent
requests for transferred data are ignored by the module until a new
data set is available. If a BTR does not occur before the end of the
next RTS period, a time–out bit is set in the BTR status area. When
set, this bit indicates that at least one data set was not transferred to
the processor. (The actual number of data sets missed is unknown.)
The time–out bit is reset at the completion of the BTR.
Set appropriate bits in the BTW data file to enable the RTS mode.
You can select RTS periods ranging from 100 milliseconds (msec) to
3.1 seconds in increments of 100msec. Refer to Table 4.C below for
actual bit settings. Note that the default mode of operation is
implemented by placing all zeroes in bits 13 through 17. Note that
binary representation of the RTS bit string is the RTS period X
100msec. For example, 900msec = 01001 = (9 X 100msec).
Data Format
Real Time Sampling