GE IC695CHS007 Serial Communications Module – PACSystems RX3i

GE IC695CHS007: Dual-Port Isolated Serial Interface for PACSystems RX3i Control Architecture

The GE IC695CHS007 is a two-channel serial communications module engineered for the PACSystems RX3i universal backplane. It occupies a single I/O slot and delivers two fully independent, optically isolated serial ports configurable as RS-232, RS-485, or RS-422 interfaces. Within a distributed control loop, this module functions as the deterministic serial gateway between the RX3i CPU and field-level devices — including Modbus RTU instruments, variable-frequency drives, operator terminals, and legacy SCADA nodes — without requiring an external serial converter or protocol bridge.

Each port operates independently at baud rates from 300 bps to 115,200 bps, with hardware-selectable line mode via onboard jumpers and software-level protocol assignment through GE Proficy Machine Edition (PME). The module draws power exclusively from the RX3i backplane bus, eliminating the need for external 24 VDC supply wiring to the communications layer. Its optical isolation barrier — rated at 500 V DC between the field-side signal lines and the backplane logic — prevents ground-loop currents from propagating into the CPU’s data bus, a critical design requirement in high-noise environments such as motor control centers, substations, and petrochemical process areas.

The IC695CHS007 supports the following protocol stacks natively: Modbus RTU (master and slave), SNP (Serial Network Protocol), SNPX (extended SNP), Serial I/O (raw byte streaming), and user-defined framing via PME’s serial I/O configuration blocks. This protocol flexibility allows a single module to simultaneously serve a Modbus RTU field instrument on Port 1 and an SNP-linked HMI panel on Port 2, reducing slot consumption and simplifying cabinet wiring.

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Technical Parameters

Hardware Logical Analysis

The IC695CHS007 implements a dedicated UART controller per port, decoupled from the RX3i CPU’s main backplane arbitration cycle. This architecture means serial frame assembly and disassembly occur asynchronously within the module’s onboard processor, and completed data blocks are transferred to the CPU’s data table via a DMA-style backplane transaction. The result is that serial communication latency does not consume CPU scan time in a linear fashion — a 115,200 bps Modbus RTU exchange with a 256-byte payload does not stall the ladder logic execution cycle.

Optical Isolation Architecture: Each port’s signal lines pass through a dual-channel optocoupler array before reaching the module’s internal logic. The isolation barrier is implemented at the physical layer, not at the protocol layer, which means it is protocol-agnostic and effective regardless of the selected interface standard (RS-232, RS-485, or RS-422). This design eliminates common-mode voltage interference — a frequent failure mode in long-cable industrial serial networks where ground potential differences between cabinet and field device can reach several volts.

RS-485 Termination and Bias: The module provides software-selectable internal termination resistors (120 Ω) for RS-485 lines, configurable through PME without requiring external resistor networks. Bias resistors maintain the bus in a defined idle state when no device is transmitting, preventing false start-bit detection during bus idle periods — a common source of framing errors in multi-drop networks with long cable runs.

EMC Design: The IC695CHS007 meets IEC 61000-4-2 (ESD), IEC 61000-4-4 (EFT/Burst), and IEC 61000-4-5 (Surge) immunity levels consistent with the PACSystems RX3i platform’s industrial EMC certification. The module’s PCB layout routes high-frequency backplane signals away from the analog-level serial signal traces, and the chassis ground connection through the backplane connector provides a low-impedance return path for induced RF currents.

Transmit Enable Control: For RS-485 half-duplex operation, the module manages the transmit-enable (TX-EN) signal automatically based on the configured protocol’s frame timing. This eliminates the need for external RS-232-to-RS-485 converters with manual or RTS-controlled TX-EN lines, which are a common source of timing-related bus contention in third-party converter implementations.

System Integration Benefits

• Zero External Power Wiring: The module draws all operating power from the RX3i backplane’s 5 V and 3.3 V rails. No separate 24 VDC terminal block wiring is required for the communications module itself, reducing cabinet wiring complexity and eliminating a potential single-point power failure for the serial interface layer.
• Dual Independent Protocol Stacks: Port 1 and Port 2 can run entirely different protocols simultaneously — for example, Modbus RTU master on Port 1 polling field transmitters while Port 2 operates as an SNP slave serving an HMI. This eliminates the need for a second module slot when two protocol domains are required.
• Native PME Integration for Diagnostics: Module status, port error counters (framing errors, parity errors, overrun counts), and communication statistics are accessible directly within the PME hardware configuration tree and the RX3i CPU’s fault table. No third-party diagnostic tool or OPC server is required to monitor serial link health.
• Deterministic Scan-Cycle Data Delivery: Received serial data is placed into the CPU’s %R or %AI reference tables at a defined point in the scan cycle, ensuring that the application program always reads a consistent, non-torn data snapshot. This is particularly important for multi-register Modbus RTU reads where partial updates could cause transient calculation errors.
• Modbus RTU Master with Configurable Poll Scheduling: In Modbus RTU master mode, the IC695CHS007 supports configurable inter-message delay, response timeout, and retry count parameters. This allows the module to accommodate slow-responding field devices (e.g., older analyzers with 500 ms response latency) without generating false communication fault alarms.
• RS-485 Multi-Drop Network Scalability: A single RS-485 port supports up to 32 addressable Modbus RTU slave devices on a single cable segment up to 1,200 m in length. For larger networks, a repeater can extend node count without requiring an additional module slot.
• Fault Isolation via Optical Barrier: Ground faults or wiring errors on the field-side serial cable cannot propagate electrical damage to the RX3i backplane or CPU. The 500 V DC isolation barrier contains fault energy at the module level, protecting the broader control system from a single-point field wiring failure.
• Brownfield Integration Without Gateway Hardware: Legacy instruments using RS-232 or RS-485 serial protocols can be integrated directly into a PACSystems RX3i system without an intermediate Ethernet-to-serial gateway device. This reduces network topology complexity, eliminates an additional IP-addressed node, and removes a potential point of latency or failure in the data path.

Quality Assurance & Global Logistics

Every IC695CHS007 unit supplied by siemensplc.com is sourced as genuine GE-manufactured hardware. Prior to dispatch, each module undergoes a structured inspection protocol: visual examination of the PCB, connector pins, and housing for mechanical damage; power-on functional verification confirming backplane communication and port initialization; and protocol-level testing on at least one port using a Modbus RTU loopback fixture to confirm UART integrity and isolation barrier continuity.

Units are shipped from our Xiamen, China warehouse using DHL Express, FedEx International Priority, or UPS Worldwide Expedited, with typical transit times of 3–7 business days to major industrial hubs in Europe, North America, Southeast Asia, and the Middle East. All shipments include commercial invoice, packing list, and certificate of origin documentation suitable for customs clearance. Export classification is handled in accordance with applicable EAR and ECCN regulations. Anti-static packaging (ESD bags + foam-lined cartons) is used for all electronic modules to prevent electrostatic discharge damage during transit.

A 12-month warranty is provided from the date of shipment. Warranty coverage includes defects in materials and workmanship under normal operating conditions as specified in the GE PACSystems RX3i Hardware Reference Manual. Dead-on-arrival (DOA) units are eligible for express replacement within 30 days of receipt, subject to return of the defective unit. Technical documentation — including the GE PACSystems RX3i Serial Communications Module User Manual (GFK-2460) — is available upon request at no charge.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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