Siemens Simatic S7 6ES7318-3EL01-0AB0

Name: Siemens Simatic S7 6ES7318-3EL01-0AB0
Brand: Siemens
SKU: 6ES7318-3EL01-0AB0
Availability: InStock

Price range: € 2.561,00 through € 5.500,00

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SKU: 6ES7318-3EL01-0AB0 Category: PLC Brand: Siemens

The SIEMENS 6ES7318-3EL01-0AB0 is a high-performance central processing unit belonging to the SIMATIC S7-300 programmable logic controller family. This CPU, designated as the CPU 318-3 PN/DP, is designed for demanding automation tasks requiring large program memory, high processing speed, and integrated communication capabilities. It operates as the central controller within an S7-300 rack configuration, executing user programs and coordinating I/O operations across local and distributed peripherals.

The CPU 318-3 PN/DP features an integrated PROFINET IO controller interface as well as a PROFIBUS DP master/slave interface, enabling direct connection to both modern Ethernet-based and legacy fieldbus networks without additional communication modules. It provides 2 MB of work memory for code and 2 MB for data, along with support for a Micro Memory Card (MMC) for program storage and retentive data backup. The unit supports MPI, PROFIBUS DP, and PROFINET IO communication protocols simultaneously, and includes a built-in web server for diagnostics. Processing performance is rated at approximately 0.1 ms per 1000 binary instructions, making it suitable for time-critical control tasks.

This CPU is widely deployed in manufacturing automation, automotive assembly lines, process industries such as chemical and water treatment plants, and material handling systems. Its combination of high memory capacity, dual fieldbus support, and fast cycle times makes it appropriate for complex machine control applications where large numbers of I/O points and coordinated motion or process sequences are required. The integrated PROFINET interface also makes it suitable for modernization projects where existing PROFIBUS installations are being extended with Ethernet-based devices.

Technical Specifications

Series / Product Family	SIMATIC S7-300
CPU Designation	CPU 318-3 PN/DP
Work Memory (Code)	2 MB
Work Memory (Data)	2 MB
Load Memory	Micro Memory Card (MMC), up to 8 MB
Processing Speed (Binary)	0.1 ms per 1000 instructions
Input / Operating Voltage	24 V DC
Power Consumption (Backplane Bus)	1.5 A at 5 V DC
Communication Interfaces	MPI/DP (integrated), PROFIBUS DP (integrated), PROFINET IO (integrated, 2-port switch)
PROFIBUS DP	Master and Slave, up to 12 Mbit/s
PROFINET IO	Controller, 100 Mbit/s
Max. Digital I/O	65536
Max. Analog I/O	4096
Operating Temperature	0 °C to +60 °C
Storage Temperature	-40 °C to +70 °C
Relative Humidity	10 % to 95 %, non-condensing
Mounting	DIN rail (S7-300 rack)
Certifications	CE, UL, cULus, ATEX (Zone 2)

Common System Event Codes

STOP with SFAIL LED: The CPU has entered STOP mode due to a system fault or programming error detected during execution.
Read the diagnostic buffer using STEP 7 or TIA Portal via the online diagnostics function. Identify the specific event causing the STOP, correct the program or hardware configuration, and perform a memory reset if required before restarting.
BF LED (Bus Fault): A fault has been detected on the PROFIBUS DP or MPI interface, typically indicating a missing or faulty slave device, incorrect baud rate, or wiring problem.
Check PROFIBUS cable continuity and termination resistors at both ends of the segment. Verify that all configured DP slaves are powered and online. Review the hardware configuration in STEP 7 for address conflicts.
BF2 LED (PROFINET Fault): A fault has been detected on the PROFINET IO interface, indicating that one or more configured IO devices are not reachable.
Verify Ethernet cable connections and switch/port status. Confirm that IO device IP addresses and device names match the hardware configuration. Check for duplicate IP addresses on the network segment.
FRCE LED (Force Active): One or more I/O addresses or variables are currently being forced to fixed values via the programming tool, which may cause unexpected machine behavior.
Connect with STEP 7 or TIA Portal and open the Force Table. Remove all active force values and confirm that the FRCE LED extinguishes before returning the system to normal operation.
Diagnostic Buffer Event: Module Access Error: The CPU cannot access a configured I/O module on the local rack or an expansion rack, typically due to a missing, failed, or incorrectly addressed module.
Check physical seating of all modules in the rack. Verify rack and slot addressing in the hardware configuration. Replace the suspect module if it does not respond after reseating.
Diagnostic Buffer Event: Cycle Time Exceeded: The OB1 scan cycle time has exceeded the configured maximum watchdog time, causing the CPU to call OB80 or transition to STOP if OB80 is not programmed.
Analyze the program for loops or communication calls causing excessive cycle time. Increase the maximum cycle time setting in the CPU properties if justified, or optimize the user program to reduce scan time.
Diagnostic Buffer Event: MMC Access Error: The CPU cannot read from or write to the inserted Micro Memory Card, which may prevent program loading or retentive data saving.
Power down the CPU and reseat the MMC. If the error persists, replace the MMC with a compatible Siemens-approved card. Ensure the card is not write-protected and has sufficient free capacity.

Frequently Asked Questions

What communication protocols does the CPU 318-3 PN/DP support?

The 6ES7318-3EL01-0AB0 supports MPI, PROFIBUS DP (master and slave), and PROFINET IO controller simultaneously. It also supports S7 communication and open communication (TCP/IP, ISO-on-TCP) via the PROFINET interface.

What programming software is required for this CPU?

This CPU is programmed using Siemens STEP 7 version 5.5 or higher (Classic). It is also compatible with TIA Portal with the appropriate STEP 7 Professional package and legacy support options.

Does this CPU require a Micro Memory Card to operate?

Yes, the CPU 318-3 PN/DP requires a Siemens Micro Memory Card (MMC) for program storage. Without an MMC inserted, the CPU cannot retain the user program after a power cycle.

Can this CPU be used as a PROFIBUS DP slave as well as a master?

Yes, the integrated PROFIBUS DP interface supports both master and slave operation. The operating mode is configured within the hardware configuration in STEP 7.

What is the maximum number of S7-300 expansion modules supported?

The CPU 318-3 PN/DP supports up to 32 modules across a maximum of 4 racks (1 central rack plus 3 expansion racks) connected via the IM 360/361 interface modules.

Troubleshooting

CPU remains in STOP mode after power-up and will not transition to RUN

Connect STEP 7 or TIA Portal online and read the diagnostic buffer to identify the last recorded event. Check whether the MMC is properly inserted and contains a valid, compatible user program.

If the diagnostic buffer indicates a configuration mismatch, download the correct hardware configuration and program. If the MMC is faulty or missing, replace it with a compatible Siemens MMC and reload the program. Perform a complete memory reset (MRES) using the mode selector switch before reloading if errors persist.

BF LED illuminated continuously with PROFIBUS slaves not communicating

Use STEP 7 hardware diagnostics to identify which DP slaves are reported as faulty. Measure bus voltage and check cable shielding and termination at both ends of the PROFIBUS segment.

Replace or repair damaged PROFIBUS cables. Ensure termination resistors are active only at the two physical ends of the bus segment. Verify that all slave addresses match the hardware configuration and that no address duplicates exist on the segment.

PROFINET IO devices shown as unavailable in diagnostics despite being powered

Check the Ethernet port link LEDs on the CPU and the IO devices. Use the Siemens Primary Setup Tool or TIA Portal device scan to verify that device names and IP addresses are correctly assigned.

Reassign device names using the online tools if they have been reset or replaced. Confirm that the network switch ports are operating at 100 Mbit/s full duplex. Replace Ethernet patch cables if link LEDs are not illuminated.

CPU cycle time increasing progressively during operation

Monitor the current cycle time using STEP 7 online diagnostics or by reading the OB1 cycle time system data. Identify which function blocks or communication calls are consuming the most processing time using the program status function.

Optimize time-intensive routines by moving non-critical processing to lower-priority OBs. Reduce the number of active PROFINET IO devices polled per cycle if communication overhead is the cause. Increase the maximum cycle time watchdog setting as a temporary measure while optimization is performed.

MMC not recognized after replacement or CPU reports load memory error

Power down the CPU and inspect the MMC slot for bent contacts or debris. Verify that the replacement MMC is a genuine Siemens-approved card of a compatible type and capacity.

Clean the MMC slot contacts carefully and reseat the card firmly. If using a new blank MMC, perform a memory reset and reload the program from STEP 7. Avoid using third-party or non-Siemens memory cards as these are not supported and may cause persistent access errors.

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

Common defects

Common defects on a Siemens Simatic S7 6ES7318-3EL01-0AB0 are:

Power Supply & Hardware

No power / PLC not starting
Blown fuses or power components
Faulty internal power supply module
Overheating due to poor cooling or fan failure
Damaged capacitors or power circuits

Input & Output (I/O) Failures

Digital inputs not responding
Analog inputs showing incorrect values
Digital outputs not switching or stuck
Burnt or damaged relay / transistor outputs
I/O modules not recognized or defective

Communication Problems

No communication with HMI or SCADA
Network issues (Profibus, Profinet, Modbus, Ethernet/IP, CAN, etc.)
Serial communication (RS232/RS485) failure
Fieldbus module malfunction
Outdated or incompatible firmware causing errors

Memory & Software Issues

Lost parameters or corrupted programs (EEPROM/Flash failure)
PLC loses program after power-down
Firmware corruption or software errors
Faulty or empty backup battery
Errors during upload/download of program

CPU & Processing Errors

PLC freezes or resets unexpectedly
CPU not responding to commands
Error messages during startup or runtime
Watchdog timer faults or internal CPU errors
Synchronization issues with other modules

Mechanical & Physical Damage

Broken PCB tracks or connectors
Corrosion due to moisture or chemicals
Contamination from dust, oil, or dirt
Burnt components or discolored boards
Poor solder joints (dry joints)

Other Failures

Faulty display or diagnostic LEDs
Non-functional buttons or keypad
Expansion modules not detected
Defective internal clock or timers
EMI/RFI noise due to damaged filters