Statement List (STL) - DCE FEL ČVUT v Praze

Integer Math Instructions
7.4 -I Subtract ACCU 1 from ACCU 2 as Integer (16-Bit)
Format
-I
Description
Status word
Example
-I (subtract 16-bit integer numbers) subtracts the contents of ACCU 1-L from the
contents of ACCU 2-L and stores the result in ACCU 1-L. The contents of ACCU 1-L
and ACCU 2-L are interpreted as 16-bit integer numbers. The instruction is executed
without regard to, and without affecting, the RLO. The status word bits CC 1, CC 0,
OS, and OV are set as a function of the result of the instruction. The instruction
produces a 16-bit integer number instead of an 32-bit integer number in the event of
an overflow/underflow.
The contents of accumulator 2 remain unchanged for CPUs with two ACCUs.
The contents of accumulator 3 are copied into accumulator 2, and the contents of
accumulator 4 are copied into accumulator 3 for CPUs with four ACCUs. The
contents of accumulator 4 remain unchanged.
See also Evaluating the Bits of the Status Word with Integer Math Instructions.
BR CC 1 CC 0 OV OS OR STA RLO /FC
writes: - x x x x - - - -
Status bit generation CC 1 CC 0 OV OS
Difference = 0 0 0 0 -
-32768 = Difference > 0 1 0 0 -
65535 >= Difference > 32767 0 1 1 1
-65535