Tdf - Compute Time Difference - Allen-Bradley MicroLogix 1400 Instruction Manual

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240 Application Specific Instructions
TDF - Compute Time
Difference
TDF
Compute Time Difference
Start N7:0
Stop N7:1
Dest N7:2
Publication 1766-RM001A-EN-P - October 2008
Instruction Operation
When the rung is true, this instruction shall read Program Checksum from
processor memory or from memory module and places the result into
Destination.
Address Levels for the operands involved in the RPC should be Word. The
result is stored to the data type of Destination. The RPC instruction
destination address supports Direct Addressing. It does not support
Indirect addressing, Indexed addressing, or Indirect Indexed Addressing.
When the Source A is 1(read from Memory Module), the memory module
should be installed in Non-Executing mode. If the Memory Module is
installed during RUN mode, the Destination value will be 0.
Instruction Type: Output
Execution Time for the RPC Instruction
Controller Data Size
MicroLogix 1400 word
long word
The Compute Time Difference Instruction (TDF) is used to calculate the
number of 10 µs ticks between any two time-stamps captured using the
RHC instruction. This lets your program determine the time difference
between any two events using a 10 µs timebase and places the result into
the Destination.
(Stop) - (Start) -> Destination
Enter the following parameters when programming this instruction:
• Start is the address of the earliest value previously captured using
the RHC instruction.
• Stop is the address of a later value captured using the RHC
instruction.
• Destination is the address to store the result of the time difference
calculation.
When Rung Is:
True False
5.9770 µs 0.2219 µs
7.2150 µs 0.2035 µs