Using library blocks in Ladder and FBD

1. Give every block its own always-true rung

A block from an installed library takes rung power on EN. On a false rung the
block isn't called, so its timers stop and its outputs hold their last value.
A motor's Run would stay on.

WRONG  |--[ AutoRun ]-----------[ UT_MOTOR  EN ]--|     block frozen when AutoRun is FALSE
RIGHT  |------------------------[ UT_MOTOR  EN ]--|     AutoCmd := AutoRun  (named pin)

2. Wire signals to named pins

Rung power only enables the block; it doesn't drive any pin. Put every signal
on the pin it belongs to: AutoCmd := AutoRun, Feedback := %IX0.3.

3. Read and write record members with contacts and coils

Record members work like any other variable:

|--[ Pump1.running ]--------------------------( Lamp_P1_Run )--|
|--[ Pump1.fltDryRun ]------------------------( Alarm_DryRun )--|
|--[ LowFloat ]-------------------------------( Steps[1].feedback )--|

4. Group slots

Sequencer steps and interlock conditions are filled with one coil each and read
with one contact each:

|--[ Conveyor2.Running ]--------------------( Steps[2].feedback )--|
|--[ Steps[2].cmd ]-------------------------( Conveyor2_Auto )-----|

5. Don't write grpXxx fields

Group blocks write those. Anything you write there is overwritten next scan.

6. Analog I/O

Until generic (ANY) pins arrive, a raw %IW value needs a UINT_TO_REAL block in
front of UT_ANALOG_IN. UT_ANALOG_OUT provides OutRaw : UINT, which connects
straight to %QW.