The SM 1221 digital input signal modules convert the level of the external digital signals from the process into the internal signal level of the S7-1200 controller.

Product Specifications :

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 8×24 V DC	SM 1221, DI 16×24 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
Standards, approvals, certificates
CE mark	Yes	Yes
CSA approval	Yes	Yes
UL approval	Yes	Yes
cULus	Yes	Yes
FM approval	Yes	Yes
RCM (formerly C-TICK)	Yes	Yes
KC approval	Yes	Yes
Marine approval	Yes	Yes
Ambient conditions
Free fall
● Fall height, max.	0.3 m; five times, in product package	0.3 m; five times, in product package
Ambient temperature during operation
● min.	-20 °C	-20 °C
● max.	60 °C	60 °C
● horizontal installation, min.	-20 °C
● horizontal installation, max.	60 °C
● vertical installation, min.	-20 °C
● vertical installation, max.	50 °C
● permissible temperature change	5°C to 55°C, 3°C / minute	5°C to 55°C, 3°C / minute
Ambient temperature during storage/transportation
● min.	-40 °C	-40 °C
● max.	70 °C	70 °C
Air pressure acc. to IEC 60068-2-13
● Storage/transport, min.	660 hPa	660 hPa
● Storage/transport, max.	1 080 hPa	1 080 hPa
Relative humidity
● Operation at 25 ℃ without condensation, max.	95 %	95 %
connection method / header
required front connector	Yes	Yes
Mechanics/material
Enclosure material (front)
● Plastic	Yes	Yes
Dimensions
Width	45 mm	45 mm
Height	100 mm	100 mm
Depth	75 mm	75 mm
Weights
Weight, approx.	170 g	210 g