FB_TWOHAND

Description Function Block

The FB_TWOHAND function block implements a two-hand circuit in which both input groups must be actuated at the same time in order to switch the output. The output can be reset only if both input groups have been set to logic 0 at the same time.

An input group can be configured as a single-channel, dual-channel, and dual-channel input with discrepancy time monitoring. It is also possible to define a time monitoring of up to 2500 ms between the two input groups. Each input can be configured both as a normally closed contact (N.C.) and as a normally open contact (N.O.) using the Negation command.

If bTwoHand2 and tDiscTime12 are deleted, then bTwohand1 is used as a 1-channel input. This operating principle also applies to the second input pair.

Table 30. VAR_INPUT

Name	Data Type	Initial Value	Description, Parameter Values
`bTwoHand1`	`SAFEBOOL`	`FALSE`	1st input channel: The Negation command can be used to specify whether a normally closed contact (safe state is requested for logic 0) or a normally open contact (safe state is requested for logic 1) is linked to this input.
`bTwoHand2`	`SAFEBOOL`	`FALSE`	2nd input channel: Same behavior as `bTwoHand1`. If the discrepancy time is not equal to 0, then the 1st and 2nd input channels are considered to be the first input group and the discrepancy time between the two channels is monitored if either of the two input channels requests the safe state.
`tDiscTime12`	`SAFETIME`	`TIME#0ms`	Discrepancy time for time monitoring of channels 1 and 2
`bTwoHand3`	`SAFEBOOL`	`FALSE`	3rd input channel or 1st input channel of the 2nd input group. Otherwise corresponds to `bTwoHand1`.
`bTwoHand4`	`SAFEBOOL`	`FALSE`	4th input channel or 2nd input channel of the 2nd input group. Otherwise corresponds to `bTwoHand2`.
`tDiscTime34`	`SAFETIME`	`TIME#0ms`	Discrepancy time for time monitoring of channels 3 and 4
`tDiscTime`	`SAFETIME`	`TIME#0ms`	Discrepancy time for time monitoring of the two input groups

Table 31. VAR_OUTPUT

Name	Data Type	Initial Value	Description, Parameter Values
`bTwoHandOut`	`SAFEBOOL`	`FALSE`	Output channel. The safe state corresponds to logic `0`.
`bError`	`SAFEBOOL`	`FALSE`	`TRUE`: The discrepancy time monitoring of a 2-channel input group has detected an error. The error must be acknowledged via the `ERR_ACK` input of the associated TwinSAFE group. `FALSE`: No error was detected.

Name

Data Type

Initial Value

Description, Parameter Values

bTwoHandOut

SAFEBOOL

FALSE

Output channel. The safe state corresponds to logic 0.

bError

SAFEBOOL

FALSE

TRUE: The discrepancy time monitoring of a 2-channel input group has detected an error. The error must be acknowledged via the ERR_ACK input of the associated TwinSAFE group.

FALSE: No error was detected.