1. Introduction

• Purpose: Monitor discrete 24 VDC field devices (switches, sensors, relays)

• Architecture: TMR (3‑2‑0) + 1oo2D voting per channel

• Safety: IEC 61508 SIL 3 / SIL 4 certified

• Channels: 60 digital inputs (24 VDC)

• Grouping: 8 isolated power groups (5 channels per group)

• Diagnostics: SOE (1 ms resolution), open/short circuit detection

• Hot‑Swap: Yes (online replacement)

2. Product Overview

• 60 × 24 VDC digital input channels (sink/source compatible)

• TMR fault‑tolerant design (three independent processing lanes)

• 1oo2D voting per channel (dual voltage measurement + σ‑δ ADC)

• Optical isolation (2500 V DC) channel‑to‑channel & channel‑to‑system

• Onboard SOE (Sequence of Events) logging (1 ms time stamp)

• Comprehensive diagnostics: open‑circuit, short‑circuit, fault injection

• Hot‑swap capability (no system shutdown required)

• Conformal coated variant (T8402C) available for harsh environments

3. Specifications

3.1 Mechanical

• Form Factor: T8000 chassis module (84 mm wide, 6U)

• Dimensions (H×W×D): 255 mm × 84 mm × 210 mm

• Weight: 1.8 kg (3.97 lbs)

• Mounting: T8100 / T8400 chassis slots (1–16)

• Connectors: Front‑panel terminal blocks (field inputs)

• PCB Protection: T8402 = standard; T8402C = conformal coated (acrylic)

3.2 Electrical

• System Supply: 20–32 V DC (nominal 24 V DC)

• Power Consumption: ≤ 6 W

• Input Channels: 60 × 24 VDC digital inputs

• Input Voltage Range: 18–32 V DC (logic 1); <5 V DC (logic 0)

• Input Current: ~6 mA per channel (at 24 V DC)

• Input Type: Sink (NPN) / Source (PNP) configurable

• Isolation: 2500 V DC optical barrier (channel‑channel, channel‑system)

• Grouping: 8 isolated power groups (5 channels per group)

• Backplane Interface: Trusted Backplane Bus (TBB), TMR

3.3 Functional

• Voting: 1oo2D per channel (dual measurement + comparison)

• SOE Resolution: 1 ms (per channel state change)

• Diagnostics:

  • Open‑circuit detection (per channel)

  • Short‑circuit detection (per group)

  • Onboard BIST (Built‑In Self‑Test)

  • Fault logging to system HMI

• Response Time: ≤ 2 ms (channel to backplane)

• Data Integrity: BER < 10⁻¹²

3.4 Environmental

• Operating Temp:

  • T8402: 0 °C to +60 °C

  • T8402C: –40 °C to +70 °C

• Storage Temp: –40 °C to +85 °C

• Humidity: 5–95 % RH, non‑condensing

• Altitude: ≤ 2000 m

• Vibration: IEC 60068‑2‑6 (1 g, 10–150 Hz)

• Shock: IEC 60068‑2‑27 (15 g, 11 ms)

• EMC: IEC 61000‑6‑2 / 6‑4 (industrial immunity)

3.5 Safety & Certification

• Safety Standard: IEC 61508 SIL 3 / SIL 4

• Certifications: CE, UL, CSA, ATEX II 3G Ex ec IIC T4 Gc, IECEx

• Fault Tolerance: TMR (3‑2‑0), 1oo2D per channel

• PFHd: < 1.0 × 10⁻⁹ / h (SIL 4)

4. Front Panel & Indicators

4.1 Front Panel LEDs

• PWR (Green): On = Module power OK; Off = No power

• RUN (Green): On = Module active; Flashing = Initialization

• FAULT (Red): On = Module/channel fault; Flashing = Minor fault

• COM (Green): Flashing = Backplane communication active

4.2 Front Panel Connectors

• TB1–TB8: 8 × terminal blocks (each 5 channels, 24 VDC inputs)

• FG: Functional Ground (chassis earth)

5. Compatibility & System Architecture

5.1 Compatible Chassis

• T8100: Trusted Processor Chassis

• T8400: Trusted Controller Chassis

5.2 Compatible Controllers

• T8111C: Trusted Processor Module

• T8151C: Trusted Safety Processor Module

5.3 System Topology (TMR)

• Field Devices → T8402 (60 DI) → Trusted Backplane (TBB) → T8111C/T8151C

• Redundancy: 3 × T8402 modules (one per TMR lane) in SIL 4 systems

6. Installation

6.1 Chassis Mounting

1. Align T8402 with empty slot in T8100/T8400 chassis.

2. Insert module firmly until backplane connector seats.

3. Tighten front‑panel screws (torque 0.8–1.0 Nm).

4. Verify PWR + RUN LEDs ON after power‑up.

6.2 Field Wiring (24 VDC Inputs)

1. For each group (TB1–TB8):

   • Connect 24 VDC + to group common terminal.

   • Connect field device output to channel input terminal.

   • Connect device common to 0 VDC / GND.

2. Use 16–22 AWG stranded wire; torque terminals to 0.5–0.6 Nm.

3. For open‑circuit detection: Install line‑monitoring resistors (per channel).

4. Verify input status via system HMI after wiring.

6.3 Hot‑Swap Procedure

1. Identify faulty T8402 via FAULT LED or HMI alarm.

2. Loosen front‑panel screws; pull module out slowly.

3. Insert new T8402; tighten screws.

4. System auto‑detects new module; no shutdown required.

7. Operation & Diagnostics

• Power‑up: PWR ON; RUN flashes during self‑test (5–10 s).

• Normal Operation: PWR + RUN steady GREEN; FAULT OFF; COM flashing.

• Fault Conditions:

  • FAULT ON: Channel short/open, TMR mismatch, or module failure.

  • FAULT Flashing: Minor fault (e.g., single‑lane mismatch).

• SOE Logging: All state changes time‑stamped (1 ms) and stored in system memory.

8. Maintenance & Troubleshooting

8.1 Routine Maintenance

• Quarterly: Check LED status; verify wiring tightness.

• Annually: Inspect terminal blocks for corrosion; clean front panel.

8.2 Common Issues

• PWR LED Off: Check chassis 24 VDC supply; verify module seating.

• RUN LED Flashing: Module self‑test failed; re‑seat or replace.

• FAULT LED On:

  • Channel open: Check field wiring/device; verify line resistor.

  • Channel short: Inspect wiring for shorts; replace device.

  • TMR mismatch: Replace faulty module.

• No Input Response: Check group 24 VDC supply; verify wiring polarity.

9. Safety & Compliance

• Install only in Trusted T8000 SIS environments.

• Comply with IEC 61508 SIL 3 / SIL 4 system requirements.

• Use isolated power supplies for field 24 VDC inputs.

• Conformal coated (T8402C) for harsh environments (condensation, dust, chemicals).

10. Ordering Information

• T8402: Trusted Dual 24 VDC DI Module (60‑Ch, standard)

• T8402C: Trusted Dual 24 VDC DI Module (60‑Ch, conformal coated)

• TC‑8402: Terminal Block Cable Kit (field wiring)

• T8100: Trusted Processor Chassis

• T8400: Trusted Controller Chassis