Safety Mat (SMAT)

The purpose of the Safety Mat instruction is to indicate, through O1 (Output 1), if the safety mat is occupied.

Safety mats typically consist of two conductive plates held apart by non-conductive separators. Each conductive plate, Channel A and Channel B of the safety mat, are alternately sourced by the safety-mat instruction’s SRCA (Source A) and SRCB (Source B) outputs. Output A and Output B of the safety mat are routed to the safety mat instruction’s Channel A and Channel B inputs.

Available Languages

Ladder Diagram

Function Block

This instruction is not available in function block.

Structured Text

This instruction is not available in structured text.

Operands

The following table provides the parameters that are used to configure the instruction.

The following table explains instruction inputs. The inputs are typically used to select different modes of application operation by enabling other instructions.

1

If this input is from a

Guard I/O

input module, make sure that the input is configured as single, not Equivalent or Complementary.

2

ISO 13849-1 stipulates instruction reset function must occur on falling edge signals. to comply with ISO 13849-1 requirements, add the logic immediately before this instruction. Rename Reset_Signal tag in this example to your reset signal tag name. Then use the OSF instruction Output Bit tag as the reset source of the instruction.

The following table provides the outputs to the instruction. In many applications, the output tags may represent the state of actual field devices. They may also be internal tags used to represent machine state information for use with other instructions.

Circuit Verification Test

The Safety Mat instruction monitors the Channel A and Channel B Safety Mat Inputs. Before Output 1 can be energized, a verification of the safety mat circuit must be completed, verifying that the Source A and Source B output to Channel A and Channel B input connections are good. This process is referred to as the circuit verification test (CVT) and is identified by the shaded areas in the timing diagrams. Output 1 can be energized when the CVT test is successful and the proper Restart-Type conditions are met.

Normal Operation

Manual Restart Operation

The timing diagram illustrates the instruction being configured for manual restart. At (A), Output 1 is energized when the reset input transitions from OFF (0) to ON (1) after the CVT.

Automatic Restart Operation

The timing diagram illustrates the instruction being configured for automatic restart. At (A), Output 1 is energized 50 ms after the CVT test.

Safety Mat Occupied Operation

The timing diagram illustrates Output 1 being de-energized when the safety mat becomes occupied. At (A), the safety mat is considered occupied and Output 1 is de-energized when the Channel A and Channel B inputs are both ON (1). At (B), the Channel A and Channel B inputs follow the Source A output for as long as the safety mat is occupied.

Safety Mat Unoccupied Operation

The timing diagram illustrates the safety mat being unoccupied and the Safety Mat instruction is initializing. At (A), the Channel A and Channel B inputs begin tracking the Source A and Source B outputs. Output 1 can then be energized based on the configured Restart Type and after the CVT.

Fault Detection Operation

The instruction detects the source output to channel input open circuits and short circuits. A short circuit between Channel A and Channel B appears to the instruction as though the mat is occupied, where Output 1 is de-energized.

The timing diagram illustrates the safety mat being occupied and the connection between Source A and Channel A is open. The restart type is configured for Manual. At (A), the circuit is opened and the Channel A input stops following the Source A output. Output 1 is de-energized and the short-circuit detect delay timer is started. At (B), the timer expires and a fault is generated. At (C), the opened circuit is corrected and the fault is reset when an OFF (0) to ON (1) transition is detected on the Reset input. At (D), the Safety Mat instruction completes the CVT test, and an OFF (0) to ON (1) transition is detected on the Reset input, and Output 1 is energized.

False Rung State Behavior

When the instruction is executed on a false rung, all instruction outputs are de-energized.

Fault Codes and Corrective Actions

The fault codes are listed in hexadecimal format followed by decimal format.

Diagnostic Codes and Corrective Actions

The diagnostic codes are listed in hexadecimal format followed by decimal format.

Affects Math Status Flags

No

Major / Minor Faults

None specific to this instruction. See

Index Through Arrays

for array-indexing faults.

Execution

Example