Giddings & Lewis 502-03638-41R3 and 502-03638-41 Processor PLC Modules for Machine Control

The Giddings & Lewis 502-03638-41R3 and 502-03638-41 are processor modules used in Giddings & Lewis CNC controllers and PLC systems. These modules are integral to the control architecture of heavy-duty machine tools such as milling machines, lathes, and machining centers. They execute real-time logic, motion control algorithms, and communication tasks for factory automation.

Processor Specifications

The 502-03638-41R3 and its variant 502-03638-41 feature a high-speed 32-bit microprocessor. Clock speed typically 25 MHz for the standard model and 33 MHz for the R3 revision. Onboard RAM capacity: 512 KB for user program and data storage. Flash memory: 1 MB for firmware and parameter backup with 10-year retention. The processor includes a lithium battery (replaceable) to maintain retentive memory during power loss. Execution speed for boolean logic is less than 0.5 µs per instruction.

Differences Between -41R3 and -41

The -41R3 revision incorporates enhanced noise immunity and faster interrupt response compared to the base -41 model. It also includes improved power supply filtering for more stable operation in high-electrical-noise environments like welding lines or plasma cutting machines. The R3 version supports additional communication protocols for integration with modern HMIs. Both modules are functionally interchangeable in most backplanes, but the R3 is recommended for new retrofits. The physical dimensions and connector pinouts are identical.

Memory and Data Storage

The processor supports up to 8 MB of additional memory via expansion modules. User program memory can be partitioned into multiple blocks: main program, subroutines, interrupt routines, and data tables. The processor uses a battery-backed SRAM for retentive data; battery life is approximately 5 years under normal temperature. A status LED on the front panel alerts when battery voltage is low. The module also includes an EEPROM for storing critical machine parameters independent of battery.

Communication Ports

The processor includes two serial ports: Port 1 is RS-232 (9-pin D-sub) for programming and connection to a PC-based development environment. Port 2 is RS-422/485 ( selectable via configuration) for connecting remote I/O, operator panels, or other processors in a multi-processor configuration. Additionally, an optional Ethernet module can be attached via the expansion connector. The module also supports a proprietary Giddings & Lewis high-speed backplane bus for communication with axis control cards and I/O modules in the same rack.

I/O Capacity and Expansion

A single 502-03638-41R3 processor can control up to 4 racks of I/O, each with up to 16 I/O modules, for a total maximum of 1024 discrete I/O points and 256 analog channels. The processor scans I/O at configurable rates from 1ms to 100ms depending on system complexity. It includes dedicated hardware for high-speed counting (up to 100kHz) and pulse output (50kHz) without burdening the main CPU. Interrupt inputs latch signals for immediate response.

Mechanical and Environmental

Dimensions: 260mm x 200mm x 40mm (including faceplate and extraction handles). Weight: 1.2 kg. Mounting: Plugs into a Giddings & Lewis card rack with 96-pin DIN connector. Front panel includes a multi-segment LED display for diagnostics, three push buttons for local control, and a programming port. Operating temperature: 0°C to 55°C. Storage: -40°C to 85°C. Humidity: 10% to 95% non-condensing. The module is coated with conformal coating for chemical resistance.

Programming Environment

The processor is programmed using Giddings & Lewis WinBOL or earlier DOS-based BOL (Block-Oriented Language). Languages supported: Ladder diagram, structured text, and machine-specific motion commands. The software runs on Windows 10/11 for WinBOL. Online editing allows changes while the machine runs. The processor supports full project documentation and version control. Simulation mode is available for testing offline.

Diagnostic Features

Built-in diagnostics include power-up self-test (POST) checking RAM, ROM, and I/O bus integrity. Runtime diagnostics monitor program execution time, watchdog timer, and communication status. Error codes are displayed on the front 2-digit hex display. The processor can log the last 50 faults with timestamp. Remote diagnostics over serial port are possible using proprietary software. An auxiliary connector allows external oscilloscope connection for timing analysis.

Compatibility with Machine Tools

These processors are specifically designed for Giddings & Lewis machine controls, including the CNC 8000, 8500, and 8600 series. They replace earlier processors 502-02606 and 502-03000. The modules are also used in some remanufactured Fadal and Cincinnati Milacron machines that adopted G&L control systems. Cross-reference to replacement parts: Emerson (who acquired G&L) offers modernization kits, but many end users continue using these original processors for legacy support.

Applications

Typical applications include large vertical and horizontal machining centers, boring mills, grinding machines, and transfer lines. The processor is also used in heavy-duty robotics for auto manufacturing, wind turbine blade machining, and aerospace part fabrication. Its rugged design withstands high vibration and temperature swings found in foundry and forging environments.

Conclusion

The Giddings & Lewis 502-03638-41R3 and 502-03638-41 processor modules provide dependable control for heavy industrial machine tools. Their robust construction, extensive I/O capacity, and legacy compatibility make them valuable for maintaining production in facilities with G&L-based equipment.