SNAP PID MODULE REFERENCE
24
SNAP PID Module User’s Guide
Status Flag Word
A status flag
word
indicates the state of certain PID module parameters. A status flag word is a
single hexadecimal word, similar to a PID control word, that displays the state of status flag bits.
These bits are read-only and cannot be modified. Status flag bits are primarily used with
ioManager’s PID Module window, since OptoENET PID Module Tuner software displays this
status information in the user interface.
Reading a Status Flag
To read a hexadecimal status flag word, do the following:
1.
Break the 8-bit word into its two separate hexadecimal values.
2.
Convert each hexadecimal value into its corresponding binary data.
3.
Match the positions of each “1” in the binary data to a status flag bit.
The table below illustrates an example of these steps. Read the table from right to left to see
how you might interpret a status flag word.
This status flag word shows that bit 4, the Output Lo flag, and bit 6, the TPO Status flag, are set.
See
“Binary/Hexadecimal Conversion Chart” on page 25
for a table of binary data and equivalent
hexadecimal values.
Status Flag Bits
Output Value
Most recently calculated PID output value in raw counts.
Scantime Countdown
Time remaining until the next PID calculation is performed.
Status flag word:
0 0 0 0 0 0 50
Hexadecimal value:
5
0
Binary data:
0 1 0 1
0 0 0 0
Status flag bits:
7 6 5 4
3 2 1 0
Bit
Flag Name and Description
0
Setpoint Lo
1 = Setpoint input is below the Setpoint Lo limit, and is clamped to that value for calculating PID
output. In Auto Mode, this flag is checked when PID output is calculated. If setpoint input re-enters
the normal range, the flag will clear at the next scan time.
Variable
Description
