The Siemens SIMATIC RF250R (6GT2821-5AC10) is an ultra-compact HF RFID reader with an RS422 interface using the 3964R transmission protocol. Measuring just 50 × 50 × 30 mm and weighing 14 g, it connects to Siemens RFID communication modules — including ASM 456, ASM 475, RF160C, RF170C, RF180C, and RF182C — with cable runs up to 1000 m. Combined with an external antenna from the Siemens ANT series, this reader is designed for distributed identification tasks across large production facilities where the reader electronics are mounted in a control cabinet and the antenna is positioned at the identification point.

How Does the RS422 Interface with 3964R Protocol Work on the RF250R?

The RS422 differential interface transmits data at up to 115.2 kbit/s using the 3964R protocol with acknowledgment and retry mechanisms for reliable operation in electrically noisy environments. The reader connects via an 8-pin M12 screw connector (pin 1: +24 V, pin 2: TXD−, pin 3: 0 V, pin 4: TXD+, pin 5: RXD+, pin 6: RXD−, pin 7: unassigned, pin 8: shield). Maximum cable length between reader and communication module is 1000 m. Up to two readers can connect to a single ASM 456 or ASM 475 communication module, which then provides upstream PROFIBUS or PROFINET connectivity to the PLC.

What RFID Standards and Transponders Are Supported?

The RF250R operates at 13.56 MHz using ISO 15693 and ISO 18000-3 standards. It is compatible with Siemens SIMATIC RF200 transponders including MDS D100, D124, D126, D139, D160, D165, D200, D324, D339, D421, D424, D425, D426, D428, D460, D524, and D528 series. Maximum RF data transfer rate is 26.5 kbit/s. The reader processes one transponder at a time. Read range depends on the selected external antenna and transponder combination — larger antennas such as the ANT 18 or ANT 30 can achieve ranges up to approximately 65 mm with compatible transponders.

What Are the Installation and Mounting Considerations?

The RF250R measures 50 × 50 × 30 mm and weighs 0.014 kg, making it suitable for mounting inside control cabinets or directly on machine frames. The RS422 interface enables the reader body to be installed in a protected enclosure near the control system, while the external antenna — connected via a separate antenna cable — is positioned at the identification point. This separation is particularly valuable in applications with extreme environmental conditions at the read point (coolant spray, high heat, mechanical impact), as only the antenna needs to withstand the harsh environment while the reader electronics remain protected. The reader itself is rated IP65 and operates from −25 °C to +70 °C. A 3-color LED indicates operating status, transponder presence, and error conditions.

Frequently Asked Questions

How does the RS422 variant differ from the RS232 variant of the RF250R?

The RS422 variant (6GT2821-5AC10) uses differential signaling with the 3964R protocol and supports cable lengths up to 1000 m, connecting to RFID communication modules for PROFIBUS/PROFINET integration. The RS232 variant (6GT2821-5AC40) operates in ASCII/scan mode for direct serial connection to a single PC or terminal over shorter distances. Choose RS422 for long-distance distributed installations integrated into automation networks; choose RS232 for simple standalone serial terminal applications.

How does the RF250R RS422 compare to the RF260R RS422?

The RF250R RS422 (6GT2821-5AC10) is ultra-compact (50 × 50 × 30 mm, 14 g, IP65) and requires a separate external antenna, offering installation flexibility with the trade-off of managing two components. The RF260R RS422 (6GT2821-6AC10) is larger (75 × 75 × 41 mm, 200 g, IP67) with an integrated antenna providing up to 135 mm read range in a single housing. Choose the RF250R for confined spaces and flexible antenna placement; choose the RF260R for a self-contained solution with extended read range and IP67 protection.