7-21
Section
BCD Calculation Instructions
464
7-21-8
DOUBLE BCD SUBTRACT – SUBL(55)
Mi
: First minuend word (BCD)
IR, SR, AR, DM, HR, TC, LR, #
Su
: First subtrahend word (BCD)
IR, SR, AR, DM, HR, TC, LR, #
Ladder Symbols
Operand Data Areas
R
: First result word
IR, SR, AR, DM, HR, LR
SUBL(55)
Mi
Su
R
@SUBL(55)
Mi
Su
R
DM 6144 to DM 6655 cannot be used for R.
When the execution condition is OFF, SUBL(55) is not executed. When the
execution condition is ON, SUBL(55) subtracts CY and the 8-digit contents of Su
and Su+1 from the 8-digit value in Mi and Mi+1, and places the result in R and
R+1. If the result is negative, CY is set and the 10’s complement of the actual
result is placed in R. To convert the 10’s complement to the true result, subtract
the content of R from zero. Since an 8-digit constant cannot be directly entered,
use the BSET(71) instruction (see
7-17-4 BLOCK SET – BSET(71)
) to create an
8-digit constant.
Mi + 1
Mi
Su + 1
Su
R + 1
R
–
CY
CY
Flags
ER:
Mi, M+1,Su, or Su+1 are not BCD.
Indirectly addressed DM word is non-existent. (Content of
*
DM word is
not BCD, or the DM area boundary has been exceeded.)
CY:
ON when the result is negative, i.e., when Mi is less than Su.
EQ
:
ON when the result is 0.
Limitations
Description
