Product Overview

The 6ES7 235-0KD22-0XA8​ is the Siemens EM 235 analog input/output expansion module for the SIMATIC S7-200 PLC platform — the “CN version” denoted by the -0XA8 suffix (China-region article, electrically and firmware-identical to the -0XA0 global version, distinguished only in Siemens ordering system for regional logistics). The EM 235 is the S7-200 family’s most capable analog slice: 4 analog inputs + 1 analog output on a single 71 mm wide expansion, giving a small S7-200 node (CPU 224, 224XP, 226, etc.) the ability to read sensors and drive analog actuators without jumping to S7-300/400 or to the later S7-200 SMART generation.Each of the 4 inputs on the 6ES7 235-0KD22-0XA8​ is software-selectable per channel across a broad menu: ±10 V, ±5 V, ±2.5 V, 0–20 mA, 4–20 mA, and 0–5 V via DIP + configuration in STEP 7-Micro/WIN. Resolution scales with range — 12 bits plus sign for voltage modes, 11 bits plus sign for current modes (the current path uses an internal 250 Ω shunt, so 0–20 mA / 4–20 mA land as 0–5 V across the ADC). The single analog output on the 6ES7 235-0KD22-0XA8​ is 12-bit, jumper-selectable between ±10 V voltage mode or 4–20 mA / 0–20 mA current mode (current output is a true sourcing output, not a V-out + shunt — important for loop drives). Conversion time is ~25 µs per channel input + output cycle, which is plenty for the S7-200 scan rates these modules lived with (typical S7-200 scan 1–10 ms for small programs).The 6ES7 235-0KD22-0XA8​ connects to the S7-200 CPU via the S7-200 expansion bus — the flat 20-pin ribbon header on the right side of the CPU or preceding expansion module. Up to 7 expansions can hang off a single S7-200 CPU (mixed EM 221/222/223/231/232/235), and the EM 235 occupies one slot in that count. Addressing is automatic: the 4 AI map into AIWx registers and the 1 AO maps into AQWx, the exact starting address determined by what expansions sit left of it. Power for the 6ES7 235-0KD22-0XA8​ logic comes from the S7-200 5 V bus (drawn through the expansion header, budget ~30 mA from CPU 5 V), while the analog front-end and output driver are referenced to the 24 V DC supply that also feeds the S7-200 CPU’s sensor supply or an external 24 V rail — the EM 235 doesn’t consume significant 24 V itself, but the 4–20 mA output loop and the current-input channels need an external 24 V excitation (two-wire transmitters) or loop supply.In the automation hierarchy, the 6ES7 235-0KD22-0XA8​ sits on small-machine panels, packaging lines, textile machines, plastic extrusion zones, water-treatment skids, and building-services sub-panels that standardized on S7-200 in the 2000s–2010s. The S7-200 platform (including the CN-region articles like the 6ES7 235-0KD22-0XA8) was discontinued globally when S7-200 SMART took over the small-PLC slot, so the EM 235 now trades in the spare/NOS market. For plants sitting on S7-200 panels that “still run fine, don’t touch them,” a cold-spare 6ES7 235-0KD22-0XA8​ is the targeted life-extension buy — cheaper by orders of magnitude than migrating the panel to S7-200 SMART or S7-1200.

Technical Specifications