Chapter 5
Signal Connections
©
National Instruments Corporation
5-7
Figure 5-2.
Limit and Home Input Circuit
Caution
Excessive input voltages can cause erroneous operation and/or component
failure. Verify that your input voltage is within the specification range.
Encoder Signals
The 7344 controller offers four channels of single-ended quadrature
encoder inputs. Each channel consists of a Phase A, a Phase B, and an Index
input, as described in the following sections.
Encoder<1..4> Phase A/Phase B
The encoder inputs provide position and velocity feedback for absolute and
relative positioning of axes in any motion system configuration.
If an encoder resource is not needed for axis control, it is available for other
functions including position or velocity monitoring, digital potentiometer
encoder inputs, or as a master encoder input for master/slave (electronic
gearing) applications.
The encoder channels (Encoder <1..4>) are implemented in a FPGA and
are high performance with extended input frequency response and
advanced features such as high-speed position capture inputs and
breakpoint outputs. The encoders have a maximum count frequency of
20 MHz.
An encoder input channel converts quadrature signals on Phase A and
Phase B into 32-bit up/down counter values. Quadrature signals are
generated by optical, magnetic, laser, or electronic devices that provide two
signals, Phase A and Phase B, that are 90° out of phase. The leading phase,
A or B, determines the direction of motion. The four transition states of the
relative signal phases provide distinct pulse edges that cause count up or
count down pulses in the direction determined by the leading phase.
74HC244
1 k
Ω
1/8 W
From the external
connector limit
and home switch pins
To the limit and home
switch circuits
DGND
Vcc
3.3 k
Ω
