FX5U PID VIA INSTRUCTION — SYMBOLIC GX WORKS3 TEACHING OUTLINE
Version: 2026-08-31
Manual checkpoint: MELSEC iQ-F FX5 User's Manual (Application), JY997D55401AF

IMPORTANT
This is reviewable pseudocode, not a GX Works3 import and not a tuning prescription.
Map the exact CPU, firmware, GX Works3 release, global labels/devices, analog or
temperature module, output hardware, numeric units, process limits and safety design.

CURRENT MANUAL INSTRUCTION SHAPE
Ladder/FBD: PID (s1) (s2) (s3) (d)
Structured Text: ENO := PID(EN, s1, s2, s3, d);

s1 = device storing target value (SV), signed 16-bit
s2 = device storing measured value (PV), signed 16-bit
s3 = head device of the PID parameter range
d  = device storing output value (MV), signed 16-bit

When labels are used for these operands, the current manual requires global labels
assigned to devices. Verify the instruction manual as well as the Application manual.

PARAMETER RANGE OWNERSHIP
Normal PID control: reserve 25 devices from s3.
Limit-cycle autotune: reserve 29 devices from s3.
Step-response autotune without hunting suppression: reserve 25 devices.
Step-response autotune with hunting suppression: reserve 28 devices.

Never write to s3+7 through s3+19; the current Application manual marks them for
internal PID processing. Cross-reference the entire selected range, including indirect,
recipe, HMI, initialization and block-transfer writers.

TEACHING NUMERIC CONTRACT
PV/SV units: 0.1 degree C
PV range: 200 to 1800 = 20.0 to 180.0 degree C
SP operating band: 200 to 1200 = 20.0 to 120.0 degree C
MV units: 0.1 percent
MV limits: 0 to 1000 = 0.0 to 100.0 percent

STARTUP / CONFIGURATION
1. Confirm ConfigurationRevision matches the approved project record.
2. Prove the s3 range has no other writer.
3. Write documented TS, ACT, filter, KP, TI, KD, TD and limit settings only from the
   versioned configuration owner. Do not use example gain values as field settings.
4. Initialize requested, limited and applied MV according to the restart philosophy.
5. Leave auto-tuning flags off unless a new authorized tune sequence owns them.

CYCLIC WRAPPER
PV_Good := ChannelHealthy
           AND PV_InRange
           AND NOT PV_Stale
           AND NOT PV_ForcedOrSubstituted
           AND PlausibilityChecksPass;

AutoPermitted := AutoRequest
                 AND PV_Good
                 AND ConfigValid
                 AND HeaterAvailable
                 AND NOT BlockingFault;

When AutoPermitted is true, execute the target-supported PID instruction through its
normal documented calling pattern with current SV, PV, protected parameters and MV.
The instruction uses the configured sampling time; prove actual scan, measurement
freshness and MV update behavior under load.

When AutoPermitted is false, use the approved Manual/fallback path and prevent stale
normal-Auto calculations from causing a later bump. Tracking/initialization must be
designed and tested for the exact instruction; this outline does not invent a hidden
tieback operand that the documented FX5 PID signature does not have.

OUTPUT PATH
MV_Request := PID result before external constraints;
MV_Limited := apply approved range/rate/state limits to MV_Request;
MV_Applied := select Manual or Automatic demand, then apply heater availability and
              final output handling;

For an approved time-proportioning heater example:
Window = 8 seconds; MV_Applied = 37.5 percent; ON time = 3 seconds.
The real window, SSR/contactor type, ratings, minimum pulse and protection require an
electrical/process design. Do not switch an electromechanical contactor at scan rate.

AUTOTUNE OWNER
Use a separate state sequence: Requested -> Preconditions -> Running -> Review ->
BoundedValidation -> Accepted/Rejected -> Archived. Abort for bad/no-change PV,
timeout, process bound, sustained saturation, heater unavailable or operator stop.
Never let an HMI bit write the ACT auto-tune bits indefinitely.

TREND TOGETHER
SV, PV, PV quality/age, MV requested, MV limited, MV applied, requested/effective mode,
heater availability, saturation, sampling/update markers, auto-tune status, FX5 PID error
status/code and first-out fault on one time base.