| Article number | 6ES7221-1BF32-0XB0 | 6ES7221-1BH32-0XB0 | 
|  | Digital Input SM 1221, 8DI, 24V DC | Digital Input SM 1221, 16DI, 24V DC | 
| General information |  |  | 
| Product type designation | SM 1221, DI 8x24 V DC | SM 1221, DI 16x24 V DC | 
| Supply voltage |  |  | 
| Rated value (DC) | 24 V | 24 V | 
| permissible range, lower limit (DC) | 20.4 V | 20.4 V | 
| permissible range, upper limit (DC) | 28.8 V | 28.8 V | 
| Input current |  |  | 
| from backplane bus 5 V DC, max. | 105 mA | 130 mA | 
| Digital inputs |  |  | 
| ● from load voltage L+ (without load), max. | 4 mA; per channel | 4 mA; per channel | 
| output voltage / header |  |  | 
| supply voltage of the transmitters / header |  |  | 
| ● product function / supply voltage for transmitters | Yes | Yes | 
| Power loss |  |  | 
| Power loss, typ. | 1.5 W | 2.5 W | 
| Digital inputs |  |  | 
| Number of digital inputs | 8 | 16 | 
| ● in groups of | 2 | 4 | 
| Input characteristic curve in accordance with IEC 61131, type 1 | Yes | Yes | 
| Number of simultaneously controllable inputs |  |  | 
| all mounting positions |  |  | 
| — up to 40 °C, max. | 8 | 16 | 
| horizontal installation |  |  | 
| — up to 40 °C, max. | 8 | 16 | 
| — up to 50 °C, max. | 8 | 16 | 
| vertical installation |  |  | 
| — up to 40 °C, max. | 8 | 16 | 
| Input voltage |  |  | 
| ● Rated value (DC) | 24 V | 24 V | 
| ● for signal "0" | 5 V DC at 1 mA | 5 V DC at 1 mA | 
| ● for signal "1" | 15 V DC at 2.5 mA | 15 V DC at 2.5 mA | 
| Input current |  |  | 
| ● for signal "0", max. (permissible quiescent current) | 1 mA | 1 mA | 
| ● for signal "1", min. | 2.5 mA | 2.5 mA | 
| ● for signal "1", typ. | 4 mA | 4 mA | 
| Input delay (for rated value of input voltage) |  |  | 
| for standard inputs |  |  | 
| — parameterizable | Yes; 0.2 ms, 0.4 ms, 0.8 ms, 1.6 ms, 3.2 ms, 6.4 ms and 12.8 ms, selectable in groups of four | Yes; 0.2 ms, 0.4 ms, 0.8 ms, 1.6 ms, 3.2 ms, 6.4 ms and 12.8 ms, selectable in groups of four | 
| for interrupt inputs |  |  | 
| — parameterizable | Yes | Yes | 
| Cable length |  |  | 
| ● shielded, max. | 500 m | 500 m | 
| ● unshielded, max. | 300 m | 300 m | 
| Interrupts/diagnostics/status information |  |  | 
| Alarms |  |  | 
| ● Diagnostic alarm | Yes | Yes | 
| Diagnostics indication LED |  |  | 
| ● for status of the inputs | Yes | Yes | 
| Potential separation |  |  | 
| Potential separation digital inputs |  |  | 
| ● between the channels, in groups of | 2 | 4 | 
| Degree and class of protection |  |  | 
| IP degree of protection | IP20 | IP20 |