6ES7350-2AH00-0AE0 SIMATIC S7-300 FM 350-2

SKU: 6ES7350-2AH00-0AE0 Category: PLC

Description
Additional information

The Siemens SIMATIC S7-300 FM 350-2 (part number 6ES7350-2AH00-0AE0) is a high-speed counter and positioning function module designed for use within the S7-300 programmable logic controller family. It belongs to the FM 350 series of intelligent function modules and is capable of processing encoder signals and performing counting, measuring, and positioning tasks independently of the CPU cycle time. The module offloads time-critical counting and positioning operations from the main CPU, enabling faster and more deterministic response to encoder inputs.

The FM 350-2 supports eight independent counter channels, each capable of operating in counting, frequency measurement, or period measurement mode. It accepts 24 V DC incremental encoder signals and provides digital outputs that can be used for direct control of actuators based on counter comparator values. The module communicates with the S7-300 CPU via the internal S7-300 backplane bus and is configured and programmed using the STEP 7 software environment with the dedicated FM 350-2 configuration tool. It supports up to 500 kHz counting frequency per channel and provides hardware-based comparator outputs for real-time response.

The FM 350-2 is widely used in packaging machinery, conveyor systems, printing presses, and material handling equipment where multiple high-speed counting or positioning tasks must be performed simultaneously. Its ability to handle eight channels independently makes it suitable for applications requiring synchronization of multiple axes or monitoring of several encoder-equipped drives at once. Industries such as automotive manufacturing, food and beverage processing, and logistics rely on this module for precise position detection and speed measurement tasks.

Technical Specifications

Number of Counter Channels	8
Maximum Counting Frequency	500 kHz
Encoder Input Voltage	24 V DC
Encoder Signal Type	24 V DC incremental encoder (single or dual channel)
Digital Outputs	8 (24 V DC, comparator outputs)
Digital Inputs	8 (24 V DC, gate/latch/reset functions)
Counter Resolution	32-bit
Operating Modes	Counting, frequency measurement, period measurement
Bus Interface	S7-300 backplane bus
Supply Voltage	24 V DC (via backplane and front connector)
Operating Temperature	0 °C to +60 °C
Storage Temperature	-40 °C to +70 °C
Relative Humidity	10 % to 95 % (non-condensing)
Dimensions (W x H x D)	40 mm x 125 mm x 120 mm
Certifications	CE, UL, cULus
Series/Product Family	SIMATIC S7-300 FM 350

Common Diagnostic Codes

Fault Code 1: Configuration error: The module configuration stored in the CPU does not match the actual module inserted in the slot.
Re-configure the module in STEP 7 and perform a new download to the CPU. Verify the correct module is installed in the correct slot.
Fault Code 2: Front connector not plugged in or missing 24 V DC supply voltage at the front connector.
Check that the front connector is properly seated and that 24 V DC is present on the supply terminals. Measure voltage at the front connector supply pins.
Fault Code 3: Encoder wire break or short circuit detected on one or more counter channels.
Inspect encoder wiring for open circuits or short circuits. Verify encoder supply voltage and signal levels at the front connector terminals.
Fault Code 4: Counter overflow or underflow: The 32-bit counter value has exceeded its upper or lower limit.
Review the application program to ensure counter limits and gate control are configured correctly. Adjust comparator values or enable ring counter mode if appropriate.
Fault Code 5: Hardware interrupt lost: A hardware interrupt triggered by a comparator event was not processed in time by the CPU.
Reduce CPU load or increase the priority of the hardware interrupt OB (OB40). Check that the interrupt OB is present in the user program.
Fault Code 6: Module not ready or internal module fault detected during self-test at startup.
Power cycle the S7-300 rack. If the fault persists, reseat the module in the rack. If the fault continues, the module may require replacement or repair.
Fault Code 7: Parameter assignment error: Invalid or out-of-range parameters were transferred to the module during startup.
Review the FM 350-2 parameter settings in the STEP 7 configuration tool. Correct any invalid values and re-download the configuration to the CPU.

Frequently Asked Questions

How many counter channels does the FM 350-2 provide?

The FM 350-2 provides 8 independent counter channels, each configurable for counting, frequency measurement, or period measurement mode.

What type of encoder signals does the 6ES7350-2AH00-0AE0 accept?

The module accepts 24 V DC incremental encoder signals. Each channel supports single-channel or dual-channel (A/B) encoder inputs with optional gate, latch, and reset inputs.

What software is required to configure the FM 350-2?

The module is configured using Siemens STEP 7 (version 5.x) with the dedicated FM 350-2 parameter assignment tool, which is included in the STEP 7 software package or available as a separate installation.

Can the FM 350-2 operate independently of the S7-300 CPU cycle?

Yes, the FM 350-2 processes encoder signals and controls its digital outputs independently of the CPU scan cycle, enabling deterministic real-time response to high-speed counting events without CPU intervention.

What is the maximum counting frequency supported per channel?

Each of the 8 channels supports a maximum counting frequency of 500 kHz, allowing accurate measurement of high-speed encoder signals.

Troubleshooting

SF (System Fault) LED on the FM 350-2 is lit after power-on

Check the CPU diagnostic buffer in STEP 7 for module-related fault entries. Verify that the module configuration in HW Config matches the physical module and slot position.

Re-download the hardware configuration from STEP 7 to the CPU. If the SF LED remains on, check the front connector wiring and 24 V DC supply. Replace the module if an internal hardware fault is confirmed.

Counter values are not incrementing despite encoder movement

Measure the encoder output signals at the front connector terminals using an oscilloscope or multimeter. Verify that the encoder supply voltage (24 V DC) is present and that the gate input is in the enabled state.

Correct any wiring faults on the encoder signal lines. Ensure the gate input is not held in the disabled state by the application program. Verify encoder signal polarity and wiring against the FM 350-2 manual.

Digital outputs do not switch at the expected comparator values

Check the comparator values configured in the FM 350-2 parameter assignment tool and verify they are within the valid counter range. Confirm that the output enable parameter is set correctly in the module configuration.

Correct the comparator threshold values in STEP 7 and re-download the configuration. Verify that the output wiring is correct and that the load connected to the output does not exceed the rated output current.

Hardware interrupt OB (OB40) is not being called when a comparator event occurs

Verify that OB40 is present in the STEP 7 project and has been downloaded to the CPU. Check the FM 350-2 configuration to confirm that hardware interrupt generation is enabled for the relevant channel.

Add OB40 to the STEP 7 project if it is missing and re-download the program. Enable hardware interrupt output in the FM 350-2 parameter settings and ensure the CPU operating mode supports interrupt processing.

Module is not recognized by the CPU after installation

Check that the module is firmly seated in the S7-300 rack and that the rack bus connector is properly engaged. Verify the slot assignment in the STEP 7 HW Config matches the physical slot used.

Reseat the module and bus connector. Update the HW Config in STEP 7 to reflect the correct slot and re-download. If the module is still not recognized, test the module in a different rack slot or test the rack bus connector for damage.

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