MUL — Multiply

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Description

MUL (Multiply) writes the product of Source A and Source B to Dest every scan its rung is true. It is an output instruction with no state and no status bits. Use MUL to scale a reading by a gain, convert units, or turn a count of containers into a count of pieces. Do not use MUL for a scale that also needs an offset; SCP does the whole linear conversion in one instruction, and CPT handles anything longer.

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Operands

Operand	Type	Format	Valid Range	Required	Description
Source A	Any numeric tag, member, element or bit, or a literal	Tag, Tag.Member, Tag[n], Tag.bit, or a literal	Any resolvable numeric reference	Yes	The first factor.
Source B	Same as Source A	Same	Any resolvable numeric reference	Yes	The second factor.
Dest	A writable numeric tag, member or element	Tag, Tag.Member, Tag[n]	SINT, INT, DINT or REAL; not a literal, not an input pin	Yes	Where the product is written.

Literals may be whole numbers (25, -3, 0x1F) or decimals (0.0625). A BOOL source reads as 0 or 1.

Dest type. Products outgrow an INT quickly: 200 × 200 is already past 32767, and the result wraps silently with no flag and no fault. Use a DINT Dest for anything but small factors, and a REAL Dest when a factor has a fraction.

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Scan Behavior

Prescan

Nothing. Dest keeps its power-up value.

Rung-condition-in is false

The instruction does nothing. Dest holds its last value.

Rung-condition-in is true

Both sources are read, multiplied, and the product is written to Dest every scan the rung is true.

Postscan

Nothing.

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Example

Scenario: A palletiser counts boxes. Each box holds a fixed number of pieces, and the order system wants pieces.

Tags:

• Calc — Compute pieces, BOOL
• Boxes — Boxes counted, INT
• Per_Box — Pieces per box, INT
• Pieces — Total pieces, INT

Rung 1:

—] [Calc———[MUL Boxes  Per_Box  Pieces]———

Scan 1 — Calc = 0. Boxes reads 12 and Per_Box reads 24. The rung is false: Pieces holds 0.

Scan 2 — Calc = 1. 12 × 24 is written: Pieces reads 288.

An INT Dest is fine here because the largest order is a few thousand pieces. A line that counts to a hundred thousand needs Pieces declared as a DINT.

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See Also

• DIV — Divide
• SCP — Scale with Parameters (gain and offset in one instruction)
• XPY — X to the Power of Y
• CPT — Compute
• Compute Instructions — Category index

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Notes

Percent scaling. MUL Raw 0.1 Value into a REAL keeps the tenths. The same instruction into an INT Dest truncates them away.

Sign. A negative factor gives a negative product; nothing is clamped.

The block never colours. Watch the rung wire and the Dest value line.