Programming example for Basic Level

The example "Two-hand control with EDM" from the document "PLCopen – Technical Committee 5 Safety Software Technical Specification Part 2: User Examples Version 1.01 – Official Release" is used as a CODESYS Safety Extension programming example for a program in the Basic Level and illustrated as a CODESYS Safety Extension FBD implementation.

Tip

For more information about programming in the Basic Level, see the document "PLCopen - Technical Committee 5 Safety Software".

Functional description of the safety functions

The following safety functions are used in this example:

When the emergency stop button is pressed, all dangerous movements must be stopped (via SF_EmergencyStop)
Emergency stop has the highest priority. After releasing the EStop pushbutton, a reset via S0 reset is required.
The safety output is activated by pressing both pushbuttons of the two-hand control. Releasing any of the two-hand pushbuttons deactivates the safety output and stops the hazardous movement via the switching devices K1 and K2 (via SF_TwoHandControlTypeII)
The basic state and the operating state of the connected switching devices are monitored. If an error is detected, then the safety output cannot become operational. (via SF_EDM)
After switching on the safety or functional application, or after an emergency stop condition, the two-hand control has to be released and actuated again to reactivate the safety output (via SF_OutControl). To ensure this for the functional restart, the process signal of the functional application is connected to the Activate input of the two-hand control FB THC_S2_S3. (If the application process is restarted while the two-hand control is activated, then the device goes to status C0003, which signals the error that both pushbuttons are pressed when activated and prevents a restart.)

In this example, only one operating state exists.

Figure 123. Variable declaration for programming example: Two-hand control with EDM

Figure 124. Implementation for programming example: Two-hand control with EDM

Table 105. Inputs:

Name	Data Type	Description
`S1_S_EStopIn`	`SAFEBOOL`	Emergency stop button S1
`S2_S_Switch1`	`SAFEBOOL`	Switch S2 connected with pushbutton 1 of two-hand control
`S3_S_Switch2`	`SAFEBOOL`	Switch S3 connected with pushbutton 2 of two-hand control
`K1_S_EDM1`	`SAFEBOOL`	Feedback external device K1
`K2_S_EDM2`	`SAFEBOOL`	Feedback external device K2
`S0_Reset`	`BOOL`	Reset by developer with switch S0 (derived from functional application)
`Process`	`BOOL`	Release of the movement by the process (derived from the functional application)

Table 106. Outputs:

Name	Data Type	Description
`S_EDM_Out_EDM_K1_K2`	`SAFEBOOL`	Controls the actuator via `K1` and `K2`
`Error_EStop_S1`	`BOOL`	Error flag of `EStop_S1`
`Error_THC_S2_S3`	`BOOL`	Error flag of `THC_S2_S3`
`Error_OC_K1_K2`	`BOOL`	Error flag of `OC_K1_K2`
`Diag_EStop_S1`	`WORD`	Diagnostic code for `EStop_S1`, `16#8xxx`: Regular operation, `16#Cxxx` in case of error in EStop_S1
`Diag_THC_S2_S3`	`WORD`	Diagnostic code for `THC_S2_S3`, `16#8xxx`: Regular operation, `16#Cxxx` in case of error in `THC_S2_S3`
`Diag_OC_K1_K2`	`WORD`	Diagnostic code for `OC_K1_K2`, `16#8xxx`: Regular operation, `16#Cxxx` in case of error in `OC_K1_K2`

Additional notes

This example can also be used with SF_TwoHandControlTypeIII.

The input of Activate was set to TRUE for the sake of simplicity. This can be replaced by a variable in the application.

Table 107. Information about used FB parameters

Function Block	Input	Constant Value	Description
`EStop_S1`	`S_StartReset`	`FALSE`	No automatic reset when the S-PLC is started.
	`S_AutoReset`	`FALSE`	No automatic reset, reset/confirmation by developer necessary
`OC_K1_K2`	`S_StartReset`	`TRUE`	Automatic reset is allowed when the S-PLC is started.
	`S_AutoReset`	`TRUE`	Automatic reset, no reset/confirmation by developer necessary
	`Static Control`	`FALSE`	A dynamic change of the Appl_Control signal (rising edge) is requested after function block activation or a triggered safety function (`S_SafeControl` to `FALSE`)
`EDM_K1_K2`	`S_StartReset`	`FALSE`	No automatic reset when the S-PLC is started.
	`MonitoringTime`	`T#200ms`	The maximum response time of the two feedback signals `S_EDM1` and `S_EDM2`