Function blocks¶

Every block that can go into a diagram. A program is a list of block instances in execution order; an input pin takes a tag or a constant, an output pin writes a tag, and every time is in milliseconds.

This page is an index so far

Each block is listed with what it does. The pin-by-pin detail — every input, output, parameter and default — is being added block by block, in the shape shown under How a block is documented.

Timers and counters¶

Block	What it does
`TON`	On-delay. The output picks up once the input has been held for the set time.
`TOF`	Off-delay. The output holds on for the set time after the input drops.
`TP`	Pulse. A rising edge produces an output of exactly the set length, and is not retriggered.
`CTU`	Count up. A rising edge adds one; a reset clears it; the output says the count reached the preset.
`CTD`	Count down. A rising edge subtracts one; a load sets the count to the preset.
`R_TRIG`	Rising edge. True for one cycle when the input goes up.
`F_TRIG`	Falling edge. True for one cycle when the input goes down.
`SR`	Latch where setting wins.
`RS`	Latch where resetting wins.
`BLINK`	Flasher. While enabled, the output alternates between a set on time and off time.

Arithmetic, logic and comparison¶

Block	What it does
`ADD` `SUB` `MUL` `DIV`	The four operations. Dividing by zero yields zero rather than a crash.
`MIN` `MAX` `ABS`	Smaller of two, larger of two, absolute value.
`AND` `OR` `XOR` `NOT`	Boolean logic.
`GT` `GE` `LT` `LE`	Greater, greater-or-equal, less, less-or-equal.
`EQ`	Equal within a tolerance, because two measured values are never exactly equal.
`SEL`	Selector: passes one of two inputs according to a boolean.

Signal handling¶

Block	What it does
`SCALE`	Linear scaling from one range onto another.
`LIMIT`	Clamps a value between a minimum and a maximum.
`HYST`	Comparator with hysteresis — separate switch-on and switch-off thresholds.
`RAMP`	Limits how fast a value may change, in units per second.
`PT1`	First-order filter with a time constant.

Process and machine¶

Block	What it does
`PID`	Control with anti-windup, output limits and a bumpless transfer between automatic and manual. The derivative is taken from the measurement, not the error, so a step in the setpoint does not kick the output. Reports saturation.
`MOTOR`	Start and stop with feedback supervision. The feedback must confirm within a timeout, or the block latches a fault and drops the command. Stop outranks start; acknowledgement works only at standstill.
`VALVE`	Open and close with end-position feedback, the same fault latching and acknowledgement. Closing outranks opening.

Motion¶

Named after PLCopen Motion, because that is the vocabulary a machine builder already has. Each is bound to an axis rather than to a tag — see FBD, axes and drives.

Block	What it does
`MC_POWER`	Switches the axis on; reports that it is in operation.
`MC_MOVEVELOCITY`	Runs at a velocity, taking a changed setpoint while running.
`MC_STOP`	Controlled stop along a deceleration ramp.
`MC_RESET`	Acknowledges an axis fault.
`MC_READACTVEL`	Reads the actual velocity.
`MC_READSTATUS`	Reads whether the axis is running or faulted.
`MC_MOVEABS` `MC_MOVEREL`	Move to a position, or by a distance.
`MC_HOME`	Reference run.
`MC_READACTPOS`	Reads the actual position.

CANopen¶

Block	What it does
`CO_CIA402`	The drive state machine itself — the building block the motion blocks and the supplied composites are made from.
`CO_SDOWRITE` `CO_SDOREAD`	Parameter access, at start-up only. Never inside the cycle.
`CO_RAMPTIME`	Acceleration and deceleration times written into the drive, and only while the axis is stopped.

Composite blocks¶

A composite is a block you build yourself out of other blocks, with its own interface. It is used like any other block and opens up when you double-click it. See FBD, axes and drives.

How a block is documented¶

Each block will get a section in this shape, so the page stays uniform as it grows:

TON¶

One sentence on what it does and when to reach for it.

Pin Direction Type Default

IN input bool

Q output bool

PT parameter time, ms 1000

Then: the behaviour at the edges — what happens on a reset, on a power cycle, when a parameter changes while running — and the mistake people make with it.