Mitsubishi FX3G Series Programming Manual page 270

FX /FX /FX /FX
3G 3U 3GC 3UC
Programming Manual - Basic & Applied Instruction Edition
Related devices
1. Relationship between the flag operation and the sign (positive or negative) of a numeric value
Device Name
M8020 Zero
M8021 Borrow
M8022 Carry
−2, −1,
−2, −1,
Cautions
1. When using a 32-bit operation instruction (DSUB or DSUBP)
When specifying word devices, a 16-bit word device on the low-order side is specified first, and then a word device
with the subsequent device number is automatically set for the high-order 16 bits.
To prevent number overlap, it is recommended to always specify an even number, for example.
2. When specifying the same device in the source and destination
The same device number can be specified for both the source and the destination.
In this case, note that the addition result changes in every operation cycle if a continuous operation type instruction
(SUB or DSUB) is used.
X001
FNC 21
SUB
Program example
1. Difference between the SUB instruction and the DEC instruction used by a program for
subtracting "1"
When SUB[P] is executed, "1" is subtracted from the contents of D0 every time X001 turns from OFF to ON.
SUB[P] instruction is similar to DECP instruction described later except the contents shown in the table below:
Flag (zero, borrow or carry)
16-bit
operation
32-bit
operation
X001
FNC 21
SUBP
X001
FNC 25
DECP
268
Series
ON : When the operation result is 0
OFF : When the operation result is other than 0
ON : When the operation result is less than −32768 (in 16-bit operation) or −2,147,483,648 (in 32-bit operation)
OFF : When the operation result is not less than −32768 (in 16-bit operation) or −2,147,483,648 (in 32-bit operation)
ON : When the operation result is more than 32767 (in 16-bit operation) or 2,147,483,647 (in 32-bit operation)
OFF : When the operation result is not more than 32767 (in 16-bit operation) or 2,147,483,647 (in 32-bit operation)
Zero flag
−32768
0,
The most
Borrow flag
significant bit of
data becomes
"1".
Zero flag
−2,147,483,648
0,
Borrow flag
D 0 K 25
[D] SUB [P] instruction
←−2←−1←0←−32768
−(+1)=
S D
−(−1)= +32767→0→+1→+2→
S D
←−2←−1←0←−2,147,483,648
−(+1)=
S D
−(−1)= +2,147,483,647→0→+1→+2→
S D
S S
1 2
D 0 K 1
D 0
10 Arithmetic and Logical Operation (+, −, ×, ÷) – FNC 20 to FNC 29
→ For the flag operations, refer to Subsection 6.5.2.
Description
Zero flag
−1,
0, 1
The most
significant bit
of data
becomes "0".
−1,
0, 1
Zero flag
(D 0) − 25→(D 0)
D 0
Operates
D
(D 0) − 1→(D 0)
D 0
(D 0) − 1→(D 0)
10.2 FNC 21 – SUB / Subtraction
Zero flag
32767, 0,
Carry flag
Zero flag
2,147,483,647, 0,
Carry flag
[D] DEC [P] instruction
Does not operate
−32,768→+32,767→+32,766
⎯
−2,147,483,648→+2,147,483,647→+2,147,483,646
⎯
1, 2
1, 2