Dual Channel Input Stop with Test and Lock (DCSTL)

The Dual Channel Input Stop with Test and Lock (DCSTL) instruction monitors dual-input safety devices whose main function is to stop safely, for example, an E-stop, light curtain, or safety gate. This instruction can only energize Output 1 when both safety inputs, Channel A and Channel B, are in the active state as determined by the Input type operand, and the correct reset actions are carried out.

In addition, this instruction has the ability to monitor a locked feedback signal from a safety device and issue a lock request to a safety device, for example a safety gate with guard locking. The Unlock Request input is used to request an electromagnetic lock or unlock. However, the hazard must not be present for the instruction to issue an unlock command. The Lock feedback input is used to determine whether or not the safety device is currently locked. To energize Output 1, the Lock Feedback input must be ON (1) in addition to the requirements of the DCST instruction.

The operation timing diagrams from the Dual Channel Input Stop (DCS) and the Dual Channel Input Stop Test (DCST) instruction are applicable to this instruction as well.

DCSTL operation diagrams, shown below, highlight the features of the lock-related operands, such as Unlock Request, Lock Feedback, Hazard Stopped, and Unlock Command.

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

This table provides the operands that are used to configure the instruction. These operands cannot be changed at runtime.

The following table explains instruction inputs. The inputs may be field device signals from input devices or derived from user logic.

1

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

This table explains instruction outputs. The outputs may be external tags (safety output modules) or internal tags for use in other logic routines

Affects Math Status Flags

No

Major/Minor Faults

None specific to this instruction. See Index Through Arrays for array-indexing faults.

Execution

Operation

Start-up Operation (Manual Cold Start)

The timing diagram illustrates Output 1 being energized when the Cold Start Type is Manual. At (A), the gate is closed and requested to lock. At (B), the gate is considered locked when the Lock Feedback transitions from OFF (0) to ON (1). At (C), Output 1 is energized when a reset is triggered. At (D), an unlock is requested when the Unlock Request signal transitions from OFF (0) to ON (1). At (E), the Unlock Command output is not energized until the Hazard Stopped input transitions from OFF (0) to ON (1). Output 1 is also de-energized at this point. At (F), Output 1 is energized again when the gate is opened, closed, and locked, and a reset is triggered.

The devices being monitored in these timing diagrams are assumed to be a safety gate with lock.

Start-up Operation (Automatic Cold Start)

The timing diagram illustrates the same behavior as the manual restart diagram, except that Cold Start Type is automatic. At (A), Output 1 is immediately energized when power is first applied because the gate is closed and locked, and the cold start type is automatic. At (B), an unlock is requested when the Unlock Request signal transitions from OFF (0) to ON (1). At (C), the Unlock Command output is not energized until the Hazard Stopped input transitions from OFF (0) to ON (1). Output 1 is also de-energized at this point. At (D), Output 1 is energized when the gate is opened, closed, and locked, and a reset is triggered.

The devices being monitored in these timing diagrams are assumed to be a safety gate with lock.

Device Not Tested After Unlock Fault (Manual Cold Start)

The timing diagram illustrates how a gate must be tested each time after it is unlocked if the Cold Start type is manual. At (A), Output 1 is energized when a reset is triggered. At (B), a fault is generated when the device is unlocked and relocked without the gate being opened. At (C), the fault is cleared when a reset is triggered. Output 1 does not become energized because a functional test has not been performed on the gate.

The devices being monitored in these timing diagrams are assumed to be a safety gate with lock.

Functional Test after Fault Operation

The timing diagram illustrates how the gate must be functionally tested after a fault occurs. At (A), Output 1 is energized when a reset is triggered with the gate closed and locked. At (B), a fault occurs because the gate is unlocked because the Unlock Request never transitioned from OFF (0) to ON (1). At (C), the fault is reset when the reset is triggered, but Output 1 cannot be energized because the gate was not functionally tested after the fault occurred. At (D), the gate has been functionally tested and the gate is opened, unlocked, and the hazard has stopped, but Output 1 cannot be energized because the gate is not locked. At (E), Output 1 is energized when a reset is triggered with the gate now locked.

The devices being monitored in these timing diagrams are assumed to be a safety gate with lock.

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.