General Purpose Inputs IN1 to IN4 Electrical Specifications
There are 4 identical general purpose digital inputs on the I/O connector. Each port exposes two pins named INxx-A and INxx-B respectively, where xx is a number ranging from 1 to 4.
This digital non-isolated differential input is polarity insensitive. Following type of devices are accepted:
- Digital Totem-Pole drivers at TTL, 5V CMOS, or 12V levels
- Potential-free contact closure (dry contacts)
- Fixed-potential contact closure (one pin of the contact at fixed potential)
The I/O controller measures the differential voltage and the differential impedance across both pins of each port sequentially. Therefore, it stimulates the external devices by applying alternatively positive and negative stimulation voltage Vs, as shown on the following diagram.
Professional Inputs 1-16 circuit
- When the measured impedance is above the impedance threshold, the I/O controller reports an OPEN state.
- When the measured impedance is below the impedance threshold, the I/O controller considers the differential voltage.
- When the measured differential voltage is above the voltage threshold, the I/O controller returns a HIGH state, else it returns a LOW state.
The impedance threshold is not adjustable. The voltage threshold is selectable among three values to determine the logic level of TTL, 5V CMOS, or 12V signals.
Hint. When you connect a low-impedance digital source (for instance a TTL gate), the capability to detect an open state can be used to detect a broken line.
Absolute max ratings
Parameter |
Symbol |
Min |
Typ. |
Max |
Units |
Absolute max voltage |
VaAbsMax, VbAbsMax |
|
|
25 |
V |
Absolute min voltage |
VaAbsMin, VbAbsMin |
-25 |
|
|
V |
The port does not operate correctly over the specified range. For normal operating conditions, refer to the DC characteristics table below.
The specification applies for both on and off power conditions.
DC characteristics
Parameter |
Test condition(*) |
Symbol |
Min |
Typ. |
Max |
Units |
AC stimulation voltage |
|
|Vs| |
|
1.67 |
|
Vptp |
DC bias voltage |
|
Vbias |
|
2.5 |
|
V |
Input voltage range |
"Logic input" operation |
Varange,Vbrange |
-7.8 |
|
12.8 |
V |
Input current
|
Va (or Vb) = -5.0 V |
Ia (or Ib) |
|
1,32 |
|
mA |
Va (or Vb) = -0.0 V |
|
0,44 |
|
mA |
||
Va (or Vb) = 2.5 V |
|
0,00 |
|
mA |
||
Va (or Vb) = 5.0 V |
|
-0,44 |
|
mA |
||
Va (or Vb) = 12.0 V |
|
-1,67 |
|
mA |
||
TTL Logic input operation (3V p.t.p signal) |
||||||
Differential voltage threshold |
Va in Vb within input voltage range |
VTTLth |
|
1.5 |
|
V |
Common-mode voltage(**) |
VTTLcmv |
-6.3 |
1.5(***) |
11.3 |
V |
|
5V CMOS logic input operation (5V p.p. signal) |
||||||
Differential voltage threshold |
Va in Vb within input voltage range |
VCMOSth |
|
2.5 |
|
V |
Common-mode voltage(**) |
VCMOScmv |
-5.3 |
2.5(***) |
10.3 |
V |
|
12V logic input operation (12V p.t.p signal) |
||||||
Differential voltage threshold |
Va in Vb within input voltage range |
V12Vth |
|
6 |
|
V |
Common-mode voltage(**) |
V12Vcmv |
-1.8 |
6(***) |
6.8 |
V |
|
Contact operation - both pins floating |
||||||
Differential impedance threshold |
Potential-free contact |
RPFth |
|
5 |
|
kΩ |
Common-mode voltage(**) |
VPFcmv |
|
2.5 |
|
V |
|
Contact operation - one pin at fixed potential |
||||||
Differential impedance threshold |
|
RFxth |
|
8.5 |
|
kΩ |
Common-mode voltage(****) |
VFXcmv |
-7.8 |
|
12.8 |
V |
(*) T = 25 °C, unless specified.
(**) Common-mode voltage = (Va + Vb)/2.
(***) One pin at GND.
(****) Common-mode voltage = voltage Va (or Vb) of pin at fixed potential.
AC characteristics
Parameter |
Test condition(*) |
Symbol |
Value |
Units |
Sampling rate |
|
f |
200 |
Hz |
Deglitching filter tap count(**) |
Filter setting at 10 ms |
tc |
2 |
Samples |
Filter setting at 100 ms |
20 |
Samples |
||
Minimum pulse width(***) |
Filter setting at 10 ms |
pwMin |
35 |
ms |
Filter setting at 100 ms |
115 |
ms |
(*) Tamb = 25°C, unless otherwise specified.
(**) 'tc' is the number of taps of the deglitching filter. The deglitching filter removes all transient input states having a number of consecutive identical samples smaller or equal to the value tc.
(***) This indicates the smallest pulse that the input lines can safely detect. This minimal value cannot be guaranteed in all circumstances; however, it can serve as guide lines for the system design.