358
Symbol Math Instructions Section 3-10
Description –C(412) subtracts the binary values in Su and CY from Mi, and outputs the
result to R. When the result is negative, it is output to R as a 2’s complement.
Flags
Precautions When –C(412) is executed, the Error Flag will turn OFF.
If as a result of the subtraction, the content of R is 0000 hex, the Equals Flag
will turn ON.
If the subtraction results in a borrow, the Carry Flag will turn ON.
If the result of subtracting a negative number and CY from a positive number
is negative (in the range 8000 to FFFF hex), the Overflow Flag will turn ON.
If the result of subtracting a positive number and CY from a negative number
is positive (in the range 0000 to 7FFF hex), the Underflow Flag will turn ON.
If as a result of the subtraction, the content of the leftmost bit of R is 1, the
Negative Flag will turn ON.
Note To clear the Carry Flag (CY), execute the Clear Carry (CLC(041)) instruction.
Examples When CIO 0.00 is ON in the following example, D110 and CY will be sub-
tracted from D100 as 4-digit signed binary values and the result will be output
to D120.
CY
–
RCY
Mi
Su
(Signed binary)
(Signed binary)
(Signed binary)
CY will turn
ON when there
is a borrow.
Name Label Operation
Error Flag ER OFF
Equals Flag = ON when the subtraction result is 0.
OFF in all other cases.
Carry Flag CY ON when the subtraction results in a borrow.
OFF in all other cases.
Overflow Flag OF ON when the result of subtracting a negative number and
CY from a positive number is in the range 8000 to FFFF
hex.
OFF in all other cases.
Underflow Flag UF ON when the result of subtracting a positive number and
CY from a negative number is in the range 0000 to 7FFF
hex.
OFF in all other cases.
Negative Flag N ON when the leftmost bit of the result is 1.
OFF in all other cases.
0.00
D100
D110
D120
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