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fanuc-dcs-safety-configuration.md

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title FANUC DCS Safety System — Configuration and Stop Modes
domain fanuc
subdomain safety
tags
dcs
safety
dual-check
emergency-stop
fence
stop-mode
safety-io
iso13849
status published
source internal-training
confidence 0.95
created 2026-07-14

Problem

FANUC DCS (Dual Check Safety) is a critical safety system that uses independent dual CPUs to monitor robot position and speed. Misconfiguration can lead to safety violations or false trips. Engineers need to understand the DCS architecture, stop modes, and safety I/O to configure it correctly.

Solution

DCS Overview

  • Independent dual-CPU monitoring of motor speed and position
  • Dual-circuit power cutoff on detection of speed/position anomalies
  • Meets ISO 13849-1 and IEC 61508 requirements
  • Default emergency stop password: 1111

DCS Function Table

Function Category PL/SIL Description
Emergency Stop Cat 4 PL e / SIL 3 Cut drive power on E-stop button (default)
Position/Speed Check Option Cat 3 / PL d / SIL 2 Monitor position and speed, cut on exceed
Joint Speed Check Option Cat 3 / PL d / SIL 2 Monitor joint speed, cut on exceed
Basic Position Check Option Cat 3 / PL d / SIL 2 Monitor Cartesian position, cut on exceed
Safety I/O Connection Option Cat 4 / PL e / SIL 3 Operate safety signals
External Mode Switch Option Cat 4 / PL e / SIL 3 Replace panel mode switch
Device Network Security Option Cat 4 / PL e / SIL 3 Network security slave device
Safety PMC Option Cat 4 / PL e / SIL 3 Safety I/O sequence via ladder
Additional Axis Servo Off Option Cat 4 / PL e / SIL 3 Cut additional axis motor power
Safety I/O Consistency Default Cat 4 / PL e / SIL 3 Cut power on I/O group inconsistency

Stop Types

Type Description
P-Stop (Power Stop) Cut servo power instantly — robot stops immediately
C-Stop (Control Stop) Decelerate then cut servo power — controlled stop
Hold Maintain servo power, decelerate to stop — softest stop

Stop Modes

Mode E-Stop Button External E-Stop Fence Open SVOFF Input
A P-Stop P-Stop C-Stop C-Stop
B P-Stop P-Stop P-Stop P-Stop
C C-Stop C-Stop C-Stop C-Stop

Safety I/O Signals

Signal Description
EES1 / EES2 External emergency stop input (dual circuit)
EAS1 / EAS2 Fence input (dual circuit)
FENCE1 / FENCE2 Fence signal (single circuit)
EMGIN1 / EMGIN2 External emergency stop (single circuit)
SSO[3] / SSO[4] DCS safety I/O

DCS Parameter Management

DCS parameters are stored in separate memory from regular parameters:

  • DCSPOS.SV — Position check parameters
  • DCSIOC.SV — I/O check parameters
  • SYSCIPS.SV — System safety parameters

To change DCS parameters:

  1. Change setting parameters first
  2. Apply to DCS parameters
  3. Enter 4-digit password (default: 1111)

Stop Distance Calculation

Stop Distance = (Motion Speed × Scan Time) + Coast Distance at Power Cutoff
  • Standard scan time: 8ms
  • Safety signal latency: 2ms (DCS I/O), 4ms (PROFINET)

Common DCS Alarms

  • SYST-212: DCS parameters need application
  • SYST-218: DCS function not available for this model
  • SRVO-048: DCS SSO external emergency stop
  • SRVO-049: DCS SSO servo disconnect
  • SRVO-223: DCS SSO error

Verification

  1. Check DCS parameter file exists: DCSPOS.SV, DCSIOC.SV
  2. Verify stop mode matches application requirements (A/B/C)
  3. Test E-stop button — should trigger correct stop type per mode
  4. Test fence signal — should trigger correct stop type per mode
  5. Verify DCS position limits match physical workspace constraints

Notes

  • DCS is a safety-critical system — changes require proper authorization and documentation
  • Always backup DCS parameters before modification
  • Stop mode B (P-Stop on everything) is the safest but most aggressive
  • Stop mode C (C-Stop on everything) is the gentlest but slowest to stop
  • PROFINET safety signals have higher latency (4ms) than DCS I/O (2ms)
  • DCS parameters are NOT included in regular parameter backup — backup separately