Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 401)

Appendix B
Programming Reference
B–6
S2/6 ➀ Message Reply
Pending Bit Status This bit is set when another node on the network has supplied
the information you requested in the MSG instruction of your
processor. This bit is cleared when the processor stores the
information and updates your MSG instruction.
S2/7 ➀ Outgoing
Message
Command
Pending Bit Status This bit is set when one or more messages in your program
are enabled and waiting, but no message is being transmitted
at the time. As soon as transmission of a message begins, the
bit is cleared. After transmission, the bit is set again if there are
further messages waiting. It remains cleared if there are no
further messages waiting.
S2/8 to S2/13 Reserved NA NA
S2/14 Math Overflow
Selection Dynamic
Configuration Set this bit when you intend to use 32-bit addition and
subtraction. When S:2/14 is set, and the result of an ADD,
SUB, MUL, or DIV instruction cannot be represented in the
destination address (underflow or overflow):
•
the overflow bit S:0/1 is set,
•
the overflow trap bit S:5/0 is set,
•
and the destination address contains the
unsigned truncated least significant 16 bits of the result.
The default condition of S:2/14 is reset (0). When S:2/14 is
reset, and the result of an ADD, SUB, MUL, or DIV instruction
cannot be represented in the destination address (underflow or
overflow):
•
the overflow bit S:0/1 is set,
•
the overflow trap bit S:5/0 is set,
•
and the destination address contains
32767 if the result is positive or – 32768 if
the result is negative.
Note that the status of bit S:2/14 has no effect on the DDV
instruction. Also, it has no effect on the math register content
when using MUL and DIV instructions.
To provide protection from inadvertent alteration of your
selection, program an unconditional OTL instruction at address
S:2/14 to ensure the new math overflow operation. Program
an unconditional OTU instruction at address S:2/14 to ensure
the original math overflow operation.
S2/15 Reserved NA NA
S3L Current Scan
Time Status The value of this byte tells you how much time elapses in a
program cycle. A program cycle includes:
Time
•
scanning the ladder program,
•
housekeeping,
•
scanning the I/O,
•
servicing of the communication channel.
The byte value is zeroed by the controller each scan,
immediately preceding the execution of rung 0 of program file
2 (main program file). The byte is incremented every 10 ms
thereafter and indicates, in 10 ms increments, the amount of
time elapsed in each scan. If this value ever equals the value
in S:3H Watchdog, a user watchdog major error is declared
(code 0022).
The resolution of the scan time value is
+
0 to –10 ms.
Example: The value 9 indicates that 80–90 ms has elapsed since
the start of the program cycle.
➀
Valid for Series C discrete only.
Reference