Equipments (Devices) > PLC200 > Program > Hardware

Block that reads the pulse value of an encoder according to a type of reading chosen, interpreting it as a fraction of revolutions.

Ladder Representation

READENC2_block

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN	BOOL	Block enabling
	Source#	BYTE	Counting source
	Pulses	DWORD UDINT	Maximum number of pulses in a turn
VAR_OUTPUT	ENO	BOOL	Output enabling
VAR_OUTPUT	Value	DINT DWORD UDINT	Counting value
VAR	READENC2_INST_0	READENC2	Instance of access to block structure

Operation

When this block has a TRUE value in EN, it gets the number of pulses counted in the encoder, as selected in Source #, and transfers them to Value. At each leading edge, Value is reset to zero. When Value increases and reaches the value of Pulses, Value receives zero. When Value decrements and tends to reach a value of -1, Value receives the value in Pulses. This way, Value always displays the result in fraction of revolutions.

When EN has FALSE value, Value remains unchanged.

The ENO value forwards to the next Ladder block the EN value after the operation is completed.

Block Flowchart

READENC2_flowchart

Example in Ladder

READENC2_example01

The above example, when identifying a leading edge on DI1, starts counting the number of pulses in the encoder connected in quadrature conformation AB. PULSES_IN_TURN is the value of pulses to complete a turn. If the value read is higher, the counting restarts from zero. If the value read is negative, counting restarts from PULSES_IN_TURN. The resulting value is stored in VALUE. The block ends with success, ENO output is activated.

Example in ST

The example below displays the instructions for applying the example above in the ST language.

VAR

PULSES_IN_TURN : DINT;

VALUE : UDINT;

READENC2_INST_0 : FB_READENC2;

END_VAR

READENC2_INST_0.EN := DI1;

READENC2_INST_0(Source:=0, Pulses:=PULSES_IN_TURN);

VALUE := READENC2_INST_0.Value;

DO1 := READENC2_INST_0.ENO;