SIEMENSTI435PLC Central Processing Unit with Integrated AC Power Supply, 22.5K Word Memory, 405-Series

Product Description

What this part is

A SIMATIC TI435 central processing unit, catalogue number 435-CPU. It is the processor of a SIMATIC TI 405 series programmable controller and it is a combined unit rather than a bare processor board: the mains power supply is built into the same housing, so it accepts 110 or 220 V AC directly and generates both the internal logic supply and a 24 V DC auxiliary output for field devices. Program memory is 22.5K words in total, of which 15.5K words are available for ladder logic.

Reading the designation

The number is written several ways on the same hardware — 435-CPU on the catalogue label, TI435 on the faceplate, CPU435 and 435CPU in service records. The 4 places it in the 405 family, the largest of the Texas Instruments 305 / 405 / 505 controller ranges. The 35 is the processor model within that family, which is what sets memory size and instruction set rather than the rack or the I/O. Siemens acquired the Texas Instruments programmable controller business in the mid-1990s and rebranded the range under the SIMATIC name, which is why identical hardware appears with either a TI or a SIMATIC mark and why the TI numbers remain the searchable ones.

What these specs mean in practice

An integrated power supply changes the slot arithmetic. Where a processor and a power supply occupy separate positions, both consume rack space and both are separate failure points and separate spares; here one unit covers both, which is why the module is physically substantial and why its AC input terminals sit on the processor itself. The 24 V DC 0.4 A auxiliary output is sized for pilot devices and a handful of sensors rather than for a bank of solenoids — field loads beyond that call for a separate supply.

The memory split is the figure to check against an existing program. Total memory of 22.5K words includes system overhead and data areas; the 15.5K ladder figure is the one that determines whether a program will load. A program written for a larger processor in the family will not fit merely because the rack and I/O match.

Quantity and configuration

1 Pc. Processor unit only. No base or rack, no I/O modules, no programming cable, no handheld or software programmer, no memory cartridge, no battery and no keyswitch key.

Installation and setup notes

The unit occupies the CPU position at the left-hand end of a 405-series base, with the AC supply landing on its own terminals and the backplane carrying logic power and the I/O bus to the remaining slots. A front keyswitch selects run and program modes, and the serial port on the faceplate is the connection for the programming device. Mass is approximately 0.86 kg. Mains input range is 85 to 132 V or 170 to 264 V AC, 50 or 60 Hz, at approximately 50 VA.

Interchange guidance

Units marked TI435-CPU, 435-CPU and CPU435 are the same hardware under different labelling conventions and are genuine interchanges. Other processors in the 405 family differ in memory size and instruction support, so they are related units rather than substitutions where an existing program has to load unchanged. The 305 and 505 families use different bases and different I/O entirely. Current Siemens production is the S7 range, which shares neither the hardware nor the programming software, so migration is a redesign rather than a module swap.