Datasheet

It251_02c_oi_e.doc / Nov-15 Page 5 / 16
2. Introduction
IT 251 has been designed as a universal encoder interface for use with incremental encoder
signals. The unit is suitable to solve the following applications:
 Level conversion from TTL / RS422 to HTL and vice-versa
 Division of quadrature encoder pulses, with adjustable division rate from 1:1 to 1:4096
 Separately programmable division of the marker pulses
 Translation from any of the three common standards of indication of the direction to any
other standard (quadrature A/B 90° or A = pulse and B = direction or A = forward impulse
and B = reverse impulse)
All settings occur from the top or bottom side of the unit, by means of four 8-position DIL
switches.
The unit is built into a compact housing with 12 screw terminals and two SUB-D-connectors and
can be mounted to DIN rails
3. Block Diagram
A
B
Z
/A
B
/B
/Z
A
Z
2x 90°
direction
Impulse forw.
Impulse rev.
A
2x 90°
direction
Impulse forw.
Impulse rev.
/A
B
/B
/Z
A
Z
/A
B
/B
/Z
Z
1
7
2
8
3
9
4
5
6
LED “State” (yellow)
Impulse A
LED “On” (green)
Power on