Siemens 6ES7221-3AD30-0XB0 SIMATIC S7-1200 SB 1221 4 DI 5VDC 200kHz Signal Board

The Siemens 6ES7221-3AD30-0XB0 is a SIMATIC S7-1200 SB 1221 signal board that adds 4 current-sourcing digital inputs rated 5 V DC with a maximum counting frequency of 200 kHz. It mounts directly onto the CPU front without consuming a rack slot, drawing 40 mA typical from the backplane bus, and reports input status via onboard diagnostic LEDs.

Certifications & Standards

• CE
• CSA
• UL
• cULus
• FM
• RCM
• KC
• Marine

Selection Notes

The 5 V input level and 200 kHz maximum frequency put this signal board ahead of the standard 24 V S7-1200 digital input modules for reading TTL-level pulse trains, incremental encoder channels, or fast sensor outputs that a 24 V input cannot resolve at speed. Because the input delay is parameterizable from 0.1 µs up to 20 ms per channel, the same board can be tuned for either fast pulse counting or debounced standard sensing without changing hardware. It plugs into the CPU front connector rather than a base-unit slot, adding 4 DI without using an expansion position on the rail.

Applications

Compact S7-1200 machine controls that need to count high-speed pulses — encoder outputs, proximity switch trains, or TTL-level sensor signals — without adding a rack module. The parameterizable input delay also lets the same board be reused for standard debounced digital sensing on space-constrained panels.