6ES7221-1BF22-0XA0 SIMATIC S7-200

SKU: 6ES7221-1BF22-0XA0 Category: PLC

Description
Additional information

The Siemens SIMATIC S7-200 series is a compact micro-PLC platform designed for small-scale automation tasks. The 6ES7221-1BF22-0XA0 is a digital input expansion module belonging to the EM 221 family, extending the I/O capacity of S7-200 CPU units. It provides 8 digital inputs operating at 24 V DC and connects directly to the S7-200 CPU via the local I/O bus.

The EM 221 module (6ES7221-1BF22-0XA0) features 8 optically isolated 24 V DC digital inputs with a rated input current of approximately 4 mA per channel. The module draws its logic power from the S7-200 CPU bus and requires a separate 24 V DC field-side supply for the input circuits. It supports standard IEC 61131-2 Type 1 and Type 3 input characteristics and is designed for direct rail or panel mounting alongside the host CPU.

This expansion module is widely used in manufacturing, material handling, building automation, and process control applications where additional digital input capacity is required beyond the onboard I/O of the S7-200 CPU. It is suitable for connecting pushbuttons, limit switches, proximity sensors, and other 24 V DC digital field devices. Its compact DIN-rail form factor makes it appropriate for space-constrained control cabinet installations.

Technical Specifications

Number of Digital Inputs	8
Input Voltage	24 V DC
Rated Input Current	4 mA per channel
Input Logic Level 1 (min)	15 V DC
Input Logic Level 0 (max)	5 V DC
Optical Isolation	Yes
Bus Supply Voltage	5 V DC (from CPU bus)
Current Consumption (5 V bus)	30 mA
Current Consumption (24 V field)	Externally supplied
Operating Temperature	0 °C to +55 °C
Storage Temperature	-40 °C to +70 °C
Relative Humidity	5 % to 95 % (non-condensing)
Mounting	DIN rail or panel mounting
Dimensions (W x H x D)	46 mm x 80 mm x 62 mm
Series/Product Family	SIMATIC S7-200 EM 221
Certifications	CE, UL, cUL

Common System Fault Codes

Fault Code 0x0001: Non-fatal CPU error: I/O module configuration mismatch detected during startup
Verify that the expansion module order and type match the hardware configuration defined in STEP 7 Micro/WIN. Re-download the configuration to the CPU.
Fault Code 0x0002: Fatal I/O bus error: loss of communication between CPU and expansion module
Check the I/O bus ribbon cable connection between the CPU and the EM 221 module. Reseat the connector and inspect for damage. Replace the cable or module if communication is not restored.
Fault Code 0x0010: Non-fatal I/O error: input module not responding on the expansion bus
Power cycle the system. Confirm the module is firmly seated on the bus connector. If the fault persists, replace the EM 221 module.
Fault Code 0x0080: CPU configuration error: more expansion modules connected than supported by the CPU variant
Reduce the number of expansion modules to within the limit supported by the specific S7-200 CPU model in use. Refer to the CPU datasheet for maximum I/O module count.
Fault Code 0x4000: Run-time I/O access error: program attempting to address input bits beyond the configured I/O range
Review the PLC program in STEP 7 Micro/WIN and ensure all input addresses referenced are within the valid range for the installed expansion modules.
Fault Code 0x0004: Non-fatal error: 24 V DC field supply missing or below threshold on input module
Measure the 24 V DC supply voltage at the input module field terminals. Verify the external power supply is functioning and wiring is correct.

Frequently Asked Questions

Which S7-200 CPU models are compatible with the 6ES7221-1BF22-0XA0?

The EM 221 module is compatible with all S7-200 CPU variants including CPU 221, CPU 222, CPU 224, CPU 224XP, and CPU 226, subject to the maximum expansion module count supported by each CPU.

Does the 6ES7221-1BF22-0XA0 require an external 24 V DC supply?

Yes, the field-side input circuits require an external 24 V DC supply connected to the module terminals. The 5 V logic power is drawn from the S7-200 CPU expansion bus.

How many EM 221 modules can be connected to a single S7-200 CPU?

The number of expansion modules depends on the CPU variant. For example, the CPU 224 supports up to 7 expansion modules, while the CPU 222 supports a maximum of 2.

What input signal types does this module accept?

The module accepts 24 V DC digital signals conforming to IEC 61131-2 Type 1 and Type 3 input characteristics, suitable for NPN and PNP sourcing/sinking sensors and switches.

What programming software is used to configure this module?

The module is configured and programmed using Siemens STEP 7 Micro/WIN software, which handles I/O addressing and hardware configuration for the S7-200 platform.

Troubleshooting

Input LEDs on the module do not illuminate when field devices are activated

Check the 24 V DC field supply voltage at the module input terminals using a multimeter. Verify wiring continuity from the field device to the module input terminal and common terminal.

Restore the 24 V DC field supply if absent or below 15 V DC. Correct any wiring faults. If the supply and wiring are correct but LEDs still do not respond, the module input circuitry may be damaged and the module should be replaced.

CPU reports an I/O configuration error on startup

Compare the physical expansion module arrangement with the hardware configuration defined in the STEP 7 Micro/WIN project. Check that module types and order match exactly.

Correct the hardware configuration in STEP 7 Micro/WIN to match the physical installation, then re-download the program and configuration to the CPU. Power cycle the system after downloading.

Intermittent loss of input signals during operation

Inspect the expansion bus ribbon cable between the CPU and the EM 221 module for damage, loose connection, or excessive bending. Check cabinet for sources of electrical noise near the module.

Reseat or replace the expansion bus ribbon cable. Ensure proper cable routing away from high-voltage conductors. Verify that the 24 V DC field supply has adequate filtering and is properly grounded.

Module inputs read incorrectly in the PLC program despite correct field wiring

Verify the input address range assigned to this module in STEP 7 Micro/WIN. Confirm the module position in the expansion chain matches the addressed I/O byte in the program.

Correct the I/O addressing in the PLC program to match the actual module position. Re-download the updated program to the CPU and verify correct operation.

Module does not power up and no LEDs are active

Measure the 5 V DC bus voltage at the expansion bus connector. Inspect the bus connector on both the CPU and the module for bent or damaged pins.

If the bus voltage is absent, check the CPU power supply output. Replace the expansion bus cable or the module if the connector is physically damaged. If the CPU bus supply is faulty, the CPU unit may require repair or replacement.

Condition	Repair, Used, Refurbished, New in box (sealed)