Siemens 545 555 1105 1106 PLC Controller
The Siemens 545-1105 and 555-1106 are central processing units belonging to the SIMATIC 505 series (originally Texas Instruments TI545/TI555). These rugged PLC controllers are designed for large-scale industrial automation, offering extensive I/O capacity, built-in communication ports, and high-speed processing. They are commonly found in power generation, water treatment, and heavy manufacturing plants.
Model Specifications: 545-1105
The 545-1105 CPU features a 16-bit processor with 128 KB user program memory (expandable to 512 KB). Scan time: 0.5 ms per 1K ladder logic. Onboard I/O includes 8 digital inputs (24V DC) and 6 relay outputs (2A). Communication ports: one RS-232 (programming), one RS-422/485 (Modbus RTU), and one Profibus DP slave interface (D-sub 9-pin). The CPU supports up to 256 local I/O points and 1024 remote I/O via Profibus.
Model Specifications: 555-1106
The 555-1106 is a higher-end model with 512 KB user memory and a floating-point math coprocessor. It includes the same I/O and communication features as the 545, plus a second Profibus DP port (master capability) and an Ethernet port (10BASE-T) for Modbus TCP. The 555-1106 can handle up to 1024 local I/O and 4096 remote I/O. Scan time is 0.2 ms per 1K steps.
Common Features
Both CPUs are housed in a metal enclosure for EMI/RFI protection. They mount on a 505 series backplane (4-slot or 8-slot). Power supply is 5V DC from backplane (545 draws 1.2A, 555 draws 1.8A). A lithium battery (type TL-5242) retains program and data for 3 years. Real-time clock with calendar is included. LED status indicators: RUN, STOP, BATT, and COM.
Programming Environment
The controllers are programmed using Siemens SoftShop (or older TI Soft) software running on Windows. Languages: ladder logic and SFC (sequential function chart). The CPUs support PID loops (up to 128 loops on 555), high-speed counters, and drum sequencers. Online editing is allowed. Firmware can be updated via serial port.
I/O Expansion
Compatible I/O modules include 505-4208 (digital input), 505-4308 (digital output), 505-4108 (analog input), and many others. Maximum rack distance: 100 m via Profibus. The CPUs also support remote I/O over fiber optic with the 505-6008 module.
Environmental Ratings
Operating temperature: 0 to 60°C; storage: -40 to 85°C. Humidity: 5% to 95% non-condensing. Vibration: 2 g (10–150 Hz). Shock: 30 g. Protection class: IP20. The units are UL 508 listed and CE marked. RoHS compliance not guaranteed (older units may contain lead).
Repair and Parts Use
These units are offered for system repair or component recovery. They can be used to replace failed CPUs in existing 505 systems, or as a source of spare parts (e.g., power connectors, backplane connectors, or display boards). No operating system password is set. Each unit has been physically inspected for major damage.
Typical Applications
Originally deployed in continuous process lines, boiler controls, and large conveyor systems. The 555-1106 is particularly suitable for motion control applications with up to 16 axes of positioning via Profibus.
Ordering Information
Model numbers: 545-1105, 555-1106. These are legacy products, no longer manufactured by Siemens. Technical documentation is available as manual “TI545/TI555 User Manual” (Pub. No. 3050434-01).
