Resolving Omron PID(190) P_ER Error on CS1G CX-Simulator

Resolving Omron PID(190) P_ER Error on CS1G CX-Simulator

1. Problem Summary

Engineers porting the Omron PID(190) expansion instruction from a C200HE reference program to a CS1G-CPU45 frequently observe the P_ER auxiliary flag (SR area CF003) latching ON while P_CY (CF004) remains OFF. The instruction halts without producing a manipulated variable (MV), and the process variable (PV) feedback loop is left open. The typical failed rung and operand contents observed in CX-Programmer are:

Observed memory image:

The combination of P_ER = ON, P_CY = OFF, and the unmodified parameter block copied from a C200HE manual points to two stacked fault conditions: an operand-mismatch error introduced by the C200HE → CS1G layout migration, and an inherent CX-Simulator execution gap.

2. Root Cause Analysis

2.1 Operand Layout Divergence Between C200HE and CS1G

Omron's PID instruction was carried forward from the C-series into CS/CJ/CP-series hardware, but the 17-word control block was extended and re-organized. The two platform generations disagree in three positions:

The most decisive word in the failed case is D206 (C+6). Decoded digit-by-digit:

• Most-significant nibble 0: PID not yet enabled via bit 15; standard control.
• Second nibble 8: invalid time-unit selector. CS1G only accepts 1 (100 ms) and 9 (1 s). The value 8 is reserved and triggers P_ER on the first PID scan.
• Trailing nibble 8: lower-order control bits (direction, MV range, derivative mode). Acceptable values.

Correcting only the second nibble from 8 to 1 yields 0818 (100 ms time base). Substituting 9 yields 0898 (1 s time base). Either value clears the parameter-validation fault on a physical CS1G-CPU45.

2.2 CX-Simulator Execution Gap

CX-Simulator (SYSMAC CX-Simulator version 1.9 / 1.91) emulates the CS1G, CJ1G, CP1H, and CP1L instruction sets, but it does not execute the PID(190) algorithm at runtime. The binary opcode is accepted, the operands are read, the parameter block is parsed — but the proportional, integral, and derivative steps are skipped. As a result:

• P_ER status in the simulator does not reliably mirror real CPU behavior.
• MV in C+13 stays at zero regardless of tuning parameters.
• Auto-tune (AT) cannot be evaluated.
• Tuning responses, overshoot, and rise time cannot be observed in simulation.

The CX-Simulator Operation Manual (W444), section 1-7 ("Comparison between CS/CJ/CP CPU and CX-Simulator"), explicitly lists unsupported instructions. PID(190) is among them. The manual states that PID validation requires physical CS1G, CJ1G, CP1H, or CP1L hardware, or a Sysmac Studio virtual CP2E controller for CP-series projects only.

2.3 P_ER Latch Semantics

Once P_ER is set by PID(190), it remains latched until the next execution of the instruction with valid operands, or until the PLC is reset. Reading CF003 alone is therefore insufficient — the engineer must verify that the execution input 0.00 remains ON, that the scan is reaching the PID rung, and that D206 was modified before the next scan.

3. Affected Hardware and Firmware

Confirm firmware on physical PLC via CX-Programmer: Online → PLC Information → Unit Version. The operand layout in this article applies to CS1G-CPU45 with unit version 2.0 or later. Earlier unit versions use a 16-word control block; the C+6 time-unit selector exists but accepts a narrower set of values.

4. PID(190) Instruction Format

The CS1G/CJ1/CP1 PID instruction has the form:

LD     0.00                  ; execution input (Always-ON)
PID(190)  10                 ; not used in CS1G (operand 1 reserved)
           D200               ; C — first word of 17-word control block
           20                 ; word-count of control area (17 minimum)
END(001)

Operand requirements:

• C (D200): first word of the 17-word control block. Must be a valid DM or CIO area word.
• Word count: minimum 17, maximum 30 on CS1G. Values below 17 trigger P_ER.
• Execution input: must transition OFF → ON at least once to start PID; the instruction then executes every scan while the input is ON.

CX-Programmer's PID Setup dialog (Settings → PID(190) Setup) auto-fills D200–D216 with CS1G defaults. When porting from C200HE, the dialog must be re-entered manually because the auto-populated values include CS1G-specific defaults (for example, default C+6 = 0000, which disables PID via bit 15).

5. Parameter Layout Reference (CS1G / CJ1 / CP1)

6. C+6 Bit Map Deep Dive

The second word of the control block, C+6 at D206, is the most error-prone word in CS1G PID migrations. Engineers must decode it as a 16-bit binary pattern, not a hex string. The complete CS1G layout per W339:

For the failed case D206 = 0888:

Hex:    0    8    8    8
Binary: 0000 1000 1000 1000
Bit 15: 0 (PID disabled at scan start)
Bit 14: 0 (no AT)
Bit 13: 0 (no bumpless)
Bits 11-8: 1000 = 8 (INVALID time-unit selector)
Bit 7: 1 (multiplier ×10)
Bit 6: 0 (reverse action)
Bit 5: 0 (0–100% MV range)
Bits 4-0: 01000 (PV range scaling disabled)

The combination of bit 11-8 = 1000 is not in the accepted list and triggers P_ER. Valid replacements:

0818: 0000 1000 0001 1000 → time unit = 100 ms, multiplier ×1, reverse, 0–100% MV
0898: 0000 1000 1001 1000 → time unit = 1 s, multiplier ×1, reverse, 0–100% MV

For 1 s sampling with ×10 multiplier: 08D8 (time-unit D = 1 s with multiplier). For 100 ms sampling with ×10 multiplier: 0818 still works because T_UNIT = 1 and bit 7 = 1 multiply to a 1 s effective sample (for tuning code that does not rescale). Always verify with the W339 control-word truth table when deviating from defaults.

7. Step-by-Step Correction Procedure

1. Confirm PID instruction form. In CX-Programmer, double-click the PID(190) rung. Verify operand 1 = D200, operand 2 = D200, operand 3 = `20` (length).
2. Recompute the control block from CS1G defaults. Open Settings → PID(190) Setup. Use the following values for the original 300-unit SP test:
   • C (D200) = `300` decimal — setpoint.
   • C+1 (D201) = `0100` hex — P band (256 decimal, 25.6% of span).
   • C+2 (D202) = `1200` hex — Ti (4608 decimal; interpret per time-unit).
   • C+3 (D203) = `0400` hex — Td (1024 decimal; interpret per time-unit).
   • C+4 (D204) = `0005` hex — sampling period.
   • C+5 (D205) = `0000` hex — MV lower limit.
   • C+6 (D206) = 0818 for 100 ms sampling or 0898 for 1 s sampling.
   • C+7 (D207) = 0FFF hex — MV upper limit (100%).
3. Enable PID. Set bit 15 of C+6 to 1. With the corrected values, the control word becomes 8818 or 8898.
4. Validate P_ER reset. Transfer the program to a physical CS1G-CPU45 (not CX-Simulator). Toggle execution input 0.00 ON. Monitor SR area CF003. It must remain OFF.
5. Capture MV and PV trend. Watch C+13 (MV output, 0–0FFF hex) and C+14 (PV scaled). Confirm the output moves in response to PV deviation.
6. Record the committed .cxp project. File → Save Project As. Name and version the file. Attach it to the maintenance record for traceability.

8. CX-Simulator Limitations and Workarounds

CX-Simulator does not execute PID(190), so P_ER behavior in the simulator does not reflect real CPU behavior. Field-proven workarounds:

• Validate on hardware. Connect CX-Programmer to a physical CS1G-CPU45 or CJ2M-CPU31 via Ethernet (port 9600) or serial (port 9600, even parity). Download the program and monitor the loop in real time.
• Use Sysmac Studio virtual controller. For CP1H projects, Sysmac Studio supports a virtual CP2E controller that executes a CP1L-compatible instruction set, including PID(190). This is the closest equivalent to a CS1G PID simulation.
• Use external simulator. Third-party OPC servers (KEPServerEX, Matrikon OPC) provide a simulated loop for tuning verification before PLC deployment.
• Disable PID before simulation. If the rung must run in CX-Simulator for code review, place a Normally Closed contact in series with the PID execution input, controlled by a simulator-only marker (e.g., W0.00 set true in the simulator project only).

9. Verification Checklist

10. Common Fault Matrix

11. Tuning Procedures

11.1 Ziegler-Nichols Open-Loop Method

1. Disable PID by clearing bit 15 of C+6.
2. Apply a manual step (e.g., 10% MV) via C+8 (manual MV word).
3. Record the PV response curve. Measure the process gain K, dead time L, and time constant T.
4. Compute initial parameters: P = 1.2·T/L, Ti = 2·L, Td = 0.5·L.
5. Enter computed values into D201, D202, D203 in the units selected by D206.
6. Set bit 15 of D206 to enable PID. Step the SP and observe response.
7. Fine-tune by reducing P (increase C+1) until oscillation damps within 2 cycles.

11.2 Auto-Tune (AT) Procedure

1. Ensure PV is stable and within 10% of SP.
2. Set C+6 bit 14 = 1 to start AT.
3. Monitor C+16 bit 0 — sets when AT completes.
4. Clear bit 14 to accept the new P, Ti, Td values written to C+1, C+2, C+3.
5. Verify the loop tracks the new SP without sustained oscillation.

11.3 Lambda Tuning for Slow Processes

For processes with large dead time (furnaces, heat exchangers), use the lambda tuning method:

• P = T / (K · (L + λ))
• Ti = T
• Td = 0

Where λ is the desired closed-loop time constant (typically 2·L to 3·L).

12. Safety and Commissioning Notes

• Start with P-only control (set Ti = 0 and Td = 0 in D202 and D203) before adding integral and derivative action.
• Use AT (auto-tune) by setting C+6 bit 14 = 1 with a stable SP and a representative disturbance.
• Verify derivative-on-PV vs derivative-on-error in C+6 bit 2 to match the process dynamics.
• Document the final P, Ti, Td values in the maintenance log alongside the SP and PV ranges.
• Save the project as a versioned .cxp file before any field modification.

13. PID Theory Reference

For background on the underlying control algorithm, including the proportional, integral, and derivative terms and their interaction, see the PID Controller & Theory Explained — National Instruments reference and the PID controller — Wikipedia article. The Omron PID(190) implementation follows the standard parallel-form equation:

MV(t) = Kp · e(t) + Ki · ∫e(t)dt + Kd · de(t)/dt

Where the band P, time Ti, and time Td relate to the standard gains as:

• Kp = 1 / P (proportional gain inverse to band)
• Ki = Kp / Ti (integral gain)
• Kd = Kp · Td (derivative gain)

Omron's band-style parameterization is convenient for tuning because increasing P softens the response without changing units, but the engineer must convert to Kp/Ki/Kd when comparing to a continuous-time model or to controller gain limits documented elsewhere in the process plant.

14. Related Omron Documentation

• CS1G/H CPU Unit Operation Manual (W339) — CS-series instruction reference, PID(190) section.
• CJ1G/H CPU Unit Operation Manual (W393) — CJ-series instruction reference.
• CP1H CPU Unit Operation Manual (W462) — CP-series instruction reference.
• CX-Simulator Operation Manual (W444) — Section 1-7 unsupported-instruction list.
• CX-Programmer Operation Manual (W463) — PID dialog reference, section 4-12.

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