The Siemens 6ES7221-1BF22-0XA8 is a spare-part digital input module from the SIMATIC S7-200 CN family, specifically the EM 221. It provides 8 digital inputs rated for 24 V DC, with a sinking-sourcing configuration. This module is designed exclusively for S7-22X CPUs and carries only CE approval.
What the ratings mean for fit
The 8 digital inputs accept 24 V DC signals, with a typical '1' signal current of 4 mA. That 4 mA figure tells you the module's input impedance is around 6 kΩ — standard for S7-200 family inputs, so it will work with most 24 V DC sensors and pushbutton contacts without loading issues. The 2 W typical power loss is drawn from the backplane bus, not an external supply; keep that within the CPU's 5 V DC budget. Physical footprint: 62 mm deep, 46 mm wide, 80 mm high. That 46 mm width is the same as the S7-200 CPU itself, so it snaps onto the DIN rail alongside other S7-200 modules without overhang. The depth matches the CPU profile, meaning it won't stick out past the front of the enclosure.
Lifecycle and sourcing reality
Marked as a spare part and listed with a current lifecycle stage, the 6ES7221-1BF22-0XA8 is not in active new-production runs — it's a service-parts holdover for installed S7-200 CN bases. The 'spare part' tag means Siemens supports it for replacements but won't push it for new designs. Sourcing is via RFQ; we quote to order against confirmed demand. No official successor order code is published for this CN variant.
Where it fits in the panel
This module snaps onto the same DIN rail as the S7-200 CPU and uses the standard S7-200 ribbon-cable bus connector. No special wiring or extra power supply needed — the 2 W backplane draw is within the CPU's capacity. The 8 inputs are grouped in a single terminal block; wire them as sinking or sourcing per the common rail connection.