Panasonic FP3 Technical Manual page 147

two's complement:
underflow:
watchdog timer:
word:
A number system used to express positive and negative numbers in binary. In this
system, the number becomes negative if the most significant bit of the data is "1".
In FP series programmable controllers, numbers are expressed using the two's
complement.
The act of going below the minimum limit in a register's capacity.
A timer that monitors processing time of the programmable controller. If the program
does not time out, the processor is assumed to be faulty.
A unit of bits which is usually executed at the same time. A word is composed of 16
bits.
8-6. Terminology
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