Accessory 24E2A
Encoder/Timer n Decode Control (MSn,MI910)
MI910 controls how the input signal for the encoder mapped to the specified node is decoded into counts.
As such, this defines the sign and magnitude of a count. The following settings may be used to decode an
input signal:
0: Pulse and direction CW
1: x1 quadrature decode CW
2: x2 quadrature decode CW
3: x4 quadrature decode CW
4: Pulse and direction CCW
5: x1 quadrature decode CCW
6: x2 quadrature decode CCW
7: x4 quadrature decode CCW
8: Internal pulse and direction
9: Not used
10: Not used
11: Not used
12: MLDT pulse timer control
(internal pulse resets timer; external pulse latches timer)
13: Not used
14: Not used
15: Not used
In any of the quadrature decode modes, PMAC is expecting two input waveforms on CHAn and CHBn,
each with approximately 50% duty cycle, and approximately one-quarter of a cycle out of phase with
each other. Times-one (x1) decode provides one count per cycle; x2 provides two counts per cycle; and
x4 provides four counts per cycle. Select x4 decode to get maximum resolution.
The clockwise (CW) and counter clockwise (CCW) options simply control which direction counts up. If
it is the wrong direction sense, simply change to the other option (e.g., from 7 to 3 or vice versa).
Warning:
If the direction sense of an encoder with a properly working servo is changed
without also changing the direction sense of the output, destabilizing positive
feedback to the servo and a dangerous runaway condition will result.
In the pulse-and-direction decode modes, PMAC is expecting the pulse train on CHAn and the direction
(sign) signal on CHBn. If the signal is unidirectional, the CHBn line can be allowed to pull up to a high
state, or it can be hardwired to a high or low state.
If MI910 is set to 8, the decoder inputs the pulse and direction signal generated by Channel n's pulse
frequency modulator (PFM) output circuitry. This permits the Compact MACRO Station to create a
phantom closed loop when driving an open-loop stepper system. No jumpers or cables are needed to do
this; the connection is entirely within the ASIC. The counter polarity matches the PFM output polarity
automatically.
If MI910 is set to 12, the timer circuitry is set up to read magnetostrictive linear displacement transducers
(MLDTs) such as Temposonics
TM
. In this mode, the timer is cleared when the PFM circuitry sends out
the excitation pulse to the sensor on PULSEn, and it is latched into the memory-mapped register when the
excitation pulse is received on CHAn.
28 Ultralite/MACRO Station Setup
To Next Page
Loading...
