SEO Title:Siemens 6ES5521-8MB11 Communications Processor

This communications processor handles data exchange for Siemens SIMATIC S5 automation systems. It manages serial communication between the PLC and external devices. Therefore, it enables connectivity with printers, scanners, and host computers.

Physical and Processor Specifications

The Siemens 6ES5521-8MB11 measures 25.0 cm in length and 18.0 cm in width. Moreover, its module weight equals approximately 0.95 kg for rack mounting. A single 48-pin male connector links this processor to the S5 backplane. Additionally, the unit includes two independent serial communication ports.

Parameter	Specification
Brand	Siemens
Full Model	6ES5521-8MB11
Category	BASIC Communications Processor
Dimensions (L x W x H)	25.0 cm x 18.0 cm x 5.5 cm (9.84″ x 7.09″ x 2.17″)
Module Weight	0.95 kg (2.09 lbs)
Backplane Interface	1 x 48-pin Male Connector (S5 Rack)
Power Supply Input	5 VDC from Backplane (0.8 A Typical)
Power Consumption	4.0 W (Typical)
Processor Type	8-bit Microcontroller (8 MHz)
Program Memory	32 kB ROM (BASIC Interpreter)
User Memory	16 kB RAM (Battery Backed)
Backup Battery	6ES5980-0UA11 (Lithium, 5 Year Life)
Communication Ports	2 x 9-pin D-Sub Male (RS-232C)
Supported Protocols	ASCII + RK512 + Custom (User Programmable)
Programming Language	BASIC (Interpreter)
Baud Rate Range	50 to 9600 baud
Data Bits	7 or 8 Bits (Configurable)
Parity Options	None, Even, Odd
Stop Bits	1 or 2 Bits
Cable Length Maximum	15 meters (49 feet) per Port
On-Board Components	1 Microcontroller + 2 UARTs + 4 Memory Chips + 2 Line Drivers + 2 Optocouplers + 6 Protection Diodes + 1 Voltage Regulator
Energy Storage	3 x 100 µF Electrolytic Capacitors (35V) + 2 x 10 µF Tantalum (25V) + 1 x CR2032 Backup Battery
Battery Backup Time	5 Years (Typical for RAM Retention)
Operating Temperature	0°C to +55°C (32°F to 131°F)
Mounting Type	S5 Rack (Single Slot)
Status Indicators	1 Green LED (Power) + 1 Green LED (Run) + 2 Yellow LEDs (Port Activity) + 1 Red LED (Fault)

Communication Processor Features and BASIC Programming

The Siemens 6ES5521-8MB11 executes user-written BASIC programs for custom communication tasks. Specifically, the built-in BASIC interpreter allows direct data manipulation and protocol conversion. In addition, the processor offloads serial communication work from the main S5 CPU. Moreover, user memory retains BASIC programs during power loss using battery backup. Consequently, this module handles complex serial data exchanges without burdening the PLC scan cycle.

Serial Port Configuration and Connectivity

Two independent RS-232C ports provide flexible connectivity for external devices. For instance, you can connect a barcode scanner to port one and a printer to port two. In addition, each port supports adjustable baud rates from 50 to 9600 baud. Furthermore, the RK512 protocol enables communication with other Siemens devices directly. Thus, this processor integrates seamlessly into existing S5 communication networks.

Energy Storage and Data Retention

This communications processor stores energy using five onboard capacitors for power filtering. Specifically, three electrolytic capacitors smooth the 5 VDC supply for stable processor operation. In addition, two tantalum capacitors provide high-frequency noise suppression for UART circuits. Furthermore, a replaceable lithium battery retains user BASIC programs and variables. Therefore, the Siemens 6ES5521-8MB11 preserves custom communication routines for up to five years.

Installation and Diagnostic Indicators

Five LED indicators provide operational status at a glance on this module. First, a green Power LED lights when the 5 VDC backplane supply is present. Second, a green Run LED flashes during normal BASIC program execution. Third, two yellow Port Activity LEDs illuminate during data transmission or reception. Finally, a red Fault LED indicates hardware errors or watchdog timeouts. Thus, you can diagnose communication status instantly without external tools.