Digital input modules can be used to connect the PLC to digital process signals. They are suitable for connecting standard switches and two-wire proximity switches (BERO).

Siemens Digital Input Modules SIMATIC S7-300 Product Specifications:

Article number	6ES7321-1BH02-0AA0	6ES7321-1BH50-0AA0	6ES7321-1BL00-0AA0	6ES7321-1BP00-0AA0	6ES7321-1BH10-0AA0
	SM321, 16DI, DC24V	SM321, 16DI, DC24V, Source Input	SM321, 32DI, DC24V	SM321, 64 DI, DC 24V, 3MS, P/M reading	SM321,16DI,DC24V, 0.05ms Input Delay.
Supply voltage
Load voltage L+
● Rated value (DC)	24 V	24 V	24 V	24 V	24 V
● permissible range, lower limit (DC)	20.4 V	20.4 V	20.4 V		20.4 V
● permissible range, upper limit (DC)	28.8 V	28.8 V	28.8 V		28.8 V
● Reverse polarity protection				Yes
Input current
from backplane bus 5 V DC, max.	10 mA	10 mA	15 mA	100 mA	110 mA
Power loss
Power loss, typ.	3.5 W	3.5 W	6.5 W	7 W	3.8 W
Digital inputs
Number of digital inputs	16	16	32	64	16
Input characteristic curve in accordance with IEC 61131, type 1	Yes	Yes	Yes	Yes	Yes
Number of simultaneously controllable inputs
all mounting positions
— up to 40 °C, max.				64
— up to 60 °C, max.				32
horizontal installation
— up to 40 °C, max.	16	16	32	64	16
— up to 60 °C, max.	16	16	16	32	16
vertical installation
— up to 40 °C, max.	16	16	32	32	16
Input voltage
● Type of input voltage	DC	DC	DC	DC	DC
● Rated value (DC)	24 V	24 V	24 V	24 V	24 V
● for signal “0”	-30 to +5 V	-5 to +30V	-30 to +5 V	-30 to +5 V	-30 to +5 V
● for signal “1”	13 to 30V	-13 to -30V	13 to 30V	13 to 30V	13 to 30V
Input current
● for signal “1”, typ.	7 mA	7 mA	7 mA	4.2 mA	7 mA
Input delay (for rated value of input voltage)
for standard inputs
— parameterizable	No	No	No	No	No
— Rated value				4.2 ms
— at “0” to “1”, min.	1.2 ms	1.2 ms	1.2 ms	1.2 ms	25 µs
— at “0” to “1”, max.	4.8 ms	4.8 ms	4.8 ms	4.8 ms	75 µs
— at “1” to “0”, min.	1.2 ms	1.2 ms	1.2 ms	1.2 ms	25 µs
— at “1” to “0”, max.	4.8 ms	4.8 ms	4.8 ms	4.8 ms	75 µs
Cable length
● shielded, max.	1 000 m	1 000 m	1 000 m	1 000 m	1 000 m
● unshielded, max.	600 m	600 m	600 m	600 m	600 m
Encoder
Connectable encoders
● 2-wire sensor	Yes	Yes	Yes	No	Yes
— permissible quiescent current (2-wire sensor), max.	1.5 mA	1.5 mA	1.5 mA		1.5 mA
Interrupts/diagnostics/status information
Alarms	No	No	No	No	No
Diagnostics function	No	No	No	No	No
Alarms
● Diagnostic alarm	No	No	No	No	No
● Hardware interrupt	No	No	No	No	No
Diagnoses
● Diagnostic information readable				No
● Wire-break				No
Diagnostics indication LED
● Group error SF (red)				No
● Status indicator digital input (green)	Yes	Yes	Yes	Yes	Yes
● Encoder supply Vs (green)				No
Potential separation
Potential separation digital inputs
● between the channels	No	No	No	No	No
● between the channels, in groups of	16	16	16	16	16
● between the channels and backplane bus	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler
Isolation
Isolation tested with	500 V DC	500 V DC	500 V DC	500 V DC	500 V DC
connection method / header
required front connector	20-pin	20-pin	40-pin	Cable: 6ES7392-4Bxx0-0AA0 terminal blocks: 6ES7392-1xN00-0AA0	20-pin
Dimensions
Width	40 mm	40 mm	40 mm	40 mm	40 mm
Height	125 mm	125 mm	125 mm	125 mm	125 mm
Depth	120 mm	120 mm	120 mm	112 mm	120 mm
Weights
Weight, approx.	200 g	200 g	260 g	230 g	200 g

Article number	6ES7321-7BH01-0AB0	6ES7321-1CH00-0AA0	6ES7321-1CH20-0AA0	6ES7321-1FH00-0AA0
	SM321, 16DI, 24V DC	SM321, 16 DI, AC/DC 24-48V, 1ch/common	SM321, 16DI, DC48-125V	SM321, 16 DI, 120/230V AC
Supply voltage
Load voltage L+
● Rated value (DC)	24 V	24 V	48 V
● permissible range, lower limit (DC)	20.4 V	24 V	48 V
● permissible range, upper limit (DC)	28.8 V	48 V	125 V
● Reverse polarity protection	Yes
Load voltage L1
● Rated value (AC)		24 V		230 V; 120/230 V AC; all load voltages must have the same phase.
● permissible range, lower limit (AC)		24 V
● permissible range, upper limit (AC)		48 V
Input current
from load voltage L+ (without load), max.	90 mA
from backplane bus 5 V DC, max.	130 mA	100 mA	40 mA	29 mA
Encoder supply
Number of outputs	2
Type of output voltage	L+ (-2.5 V)
Short-circuit protection	Yes; Electronic
additional (redundant) feed	Yes
Output current
● Rated value	120 mA
● permissible range, lower limit	0 mA
● permissible range, upper limit	150 mA
Power loss
Power loss, typ.	4 W	1.5 W; at 24 V; 2,8 W at 48 V	4.3 W	4.9 W
Digital inputs
Number of digital inputs	16	16	16	16
Input characteristic curve in accordance with IEC 61131, type 1		Yes	Yes	Yes
Input characteristic curve in accordance with IEC 61131, type 2	Yes
Number of simultaneously controllable inputs
horizontal installation
— up to 40 °C, max.	16	16	8	16
— up to 60 °C, max.	16	16	8; 6 to Ue 146 V	16
vertical installation
— up to 40 °C, max.	16	16	8	16
Input voltage
● Type of input voltage	DC	AC/DC	DC	AC
● Rated value (DC)	24 V	24 V; DC 24 or 48 V	48 V; 48 V DC to 125 V DC
● Rated value (AC)		24 V; 24 V AC or 48 V AC (0 … 63 Hz)		230 V; 120/230 V AC (47 … 63 Hz)
● for signal “0”	-30 to +5 V	-5V AC to +5V AC	-146 V DC to +15 V DC	0 to 40V
● for signal “1”	13 to 30V	14V AC to 60V AC	30 V DC to 146 V DC	79 to 264V
Input current
● for signal “0”, min.		-1 mA
● for signal “0”, max. (permissible quiescent current)		1 mA
● for signal “1”, typ.	7 mA	2.7 mA	3.5 mA	6.5 mA; (120 V, 60 Hz), 16 mA (230 V, 50 Hz)
Input delay (for rated value of input voltage)
for standard inputs
— parameterizable	Yes; 0.1 / 0.5 / 3 / 15 / 20 ms	No	No	No
— at “0” to “1”, min.		16 ms	0.1 ms	25 ms
— at “0” to “1”, max.		16 ms	3.5 ms	25 ms
— at “1” to “0”, min.			0.7 ms
— at “1” to “0”, max.		16 ms	3 ms	25 ms
Encoder connection
● Fixed current limitation for wire-break monitoring, min.	10 kΩ
● Fixed current limitation for wire-break monitoring, max.	18 kΩ
Cable length
● shielded, max.	1 000 m	1 000 m	1 000 m	1 000 m
● unshielded, max.	600 m	600 m	600 m	600 m
Encoder
Connectable encoders
● 2-wire sensor	Yes	Yes	Yes	Yes
— permissible quiescent current (2-wire sensor), max.	2 mA	1 mA	1 mA	2 mA
Interrupts/diagnostics/status information
Alarms	Yes	No	No	No
Diagnostics function	Yes; Parameterizable	No	No	No
Alarms
● Diagnostic alarm	Yes; Parameterizable	No	No	No
● Hardware interrupt	Yes; Parameterizable	No	No	No
Diagnoses
● Diagnostic information readable	Yes
● Wire-break	Yes; to I< 1 mA
Diagnostics indication LED
● Group error SF (red)	Yes	No	No	No
● Status indicator digital input (green)	Yes	Yes	Yes	Yes
● Encoder supply Vs (green)	Yes
Potential separation
Potential separation digital inputs
● between the channels	No	Yes	No	No
● between the channels, in groups of	16	1	8	4
● between the channels and backplane bus	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler
Isolation
Isolation tested with	500 V DC	1 500 V AC	1 500 V DC	4 000 V DC
connection method / header
required front connector	20-pin	40-pin	20-pin	20-pin
Dimensions
Width	40 mm	40 mm	40 mm	40 mm
Height	125 mm	125 mm	125 mm	125 mm
Depth	120 mm	120 mm	120 mm	120 mm
Weights
Weight, approx.	200 g	260 g	200 g	240 g

Article number	6ES7321-1EL00-0AA0	6ES7321-1FF01-0AA0	6ES7321-1FF10-0AA0
	SM321, 32DI, AC120V	SM321, 8DI, AC120/230V	SM321, 8 DI, AC/DC 120/230V, 1ch/common
Supply voltage
Load voltage L1
● Rated value (AC)	120 V	230 V; 120/230 V AC	230 V; 120/230 V AC; all load voltages must have the same phase.
Input current
from backplane bus 5 V DC, max.	16 mA	29 mA	100 mA
Power loss
Power loss, typ.	4 W	4.9 W	4.9 W
Digital inputs
Number of digital inputs	32	8	8
Input characteristic curve in accordance with IEC 61131, type 1		Yes	Yes
Input characteristic curve in accordance with IEC 61131, type 2	Yes
Number of simultaneously controllable inputs
horizontal installation
— up to 40 °C, max.	32
— up to 60 °C, max.	24	8	8
vertical installation
— up to 40 °C, max.	32	8	8
Input voltage
● Type of input voltage	AC	AC	AC
● Rated value (AC)	120 V; 47 … 63 Hz	230 V; 120/230 V AC (47 … 63 Hz)	120 V; 120/230 V AC (47 … 63 Hz)
● for signal “0”	0 to 20V	0 to 40V	0 to 40V
● for signal “1”	74 to 132V	79 to 264V	79 to 264V
Input current
● for signal “1”, typ.	21 mA	6.5 mA; (120 V); 11 mA (230 V)	7.5 mA; (120 V); 17.3 mA (230 V)
Input delay (for rated value of input voltage)
for standard inputs
— parameterizable	No	No	No
— at “0” to “1”, max.	15 ms	25 ms	25 ms
— at “1” to “0”, max.	25 ms	25 ms	25 ms
Cable length
● shielded, max.	1 000 m	1 000 m	1 000 m
● unshielded, max.	600 m	600 m	600 m
Encoder
Connectable encoders
● 2-wire sensor	Yes	Yes	Yes
— permissible quiescent current (2-wire sensor), max.	4 mA	2 mA	2 mA
Interrupts/diagnostics/status information
Alarms	No	No	No
Diagnostics function	No	No	No
Alarms
● Diagnostic alarm	No	No	No
● Hardware interrupt	No	No	No
Diagnostics indication LED
● Group error SF (red)	No	No	No
● Status indicator digital input (green)	Yes; per channel	Yes	Yes
Potential separation
Potential separation digital inputs
● between the channels	No	No	Yes
● between the channels, in groups of	8	2	1
● between the channels and backplane bus	Yes; Optocoupler	Yes; Optocoupler	Yes; Optocoupler
Isolation
Isolation tested with	2 500 V DC	4 000 V DC	1 500 V AC
connection method / header
required front connector	40-pin	20-pin	40-pin
Dimensions
Width	40 mm	40 mm	40 mm
Height	125 mm	125 mm	125 mm
Depth	120 mm	120 mm	120 mm
Weights
Weight, approx.	300 g	240 g	240 g