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USB Incremental Encoder Interface Hardware
Deva037 USB Encoder Interface User’s Manual
4.1.2
Input signal descriptions
The Ai & nAi, Bi & nBi inputs are differential pairs for connection to the A-phase and B-phase
quadrature outputs of an incremental encoder.
The Mi & nMi inputs are differential inputs for the channel marker signal. This function will
latch the counter reading for the relevant channel, allowing an accurate reading of the
position of a moving encoder to be made at a specific instant. The marker function does not
stop the counter itself, which is able to continue reading the encoder position and so it will
not cause the device to lose track of the system's datum position.
The Zi & nZi may be used as an alternative to the Mi & nMi inputs. In this case the driver will
zero the counter readings in software.
The inputs nLim0 and nLim1 are digital inputs intended to be used to connect normally closed
overtravel inputs.
The differential inputs use RS422 levels which accept 0V for logic low, and from +5V to +12V
for logic high. Because they are differential inputs, one input should be low when the other is
high. For Example, to trigger the marker function, set Mi input to high, and set nMi input to
low. To turn the marker function off, reverse these voltages.
An internal resistor network is provided which allows connection of single ended signals to
the non-inverting inputs.
The +/- 12V and +5V power supply pins can be used to supply the dc power requirements for
the encoders and are derived from the external power connector.
4.1.3
Renishaw probe input connections
A Renishaw probe and a footswitch and sounder can be connected via the 9-way female 'D'
connector. Connections to this socket should be made with reference to the following pin-out
table.
Pin Number
Signal
Function
1
LED C
LED cathode
2
0V
(0V)
3
LED A
LED anode
4
Probe +
Probe
5
Probe -
(0V)
6
Siren +
Siren +5V
7
Siren -
(0V)
8
Footswitch input
9
FootSw -
(0V)