Delta Tau GEO PMAC Manual Do Utilizador
Geo PMAC Drive User Manual
48
Setting Up Encoders
Software Setup
There are several parts of the software setup for the use of SSI encoders in the Geo PMAC. The first part
is the software configuration of the hardware interface to establish the clock frequency (bit rate), number
of bits, and expected data format. The second part is the processing of the received data in the encoder
conversion table (ECT). The third part is defining the use of the processed data by the motor software.
is the software configuration of the hardware interface to establish the clock frequency (bit rate), number
of bits, and expected data format. The second part is the processing of the received data in the encoder
conversion table (ECT). The third part is defining the use of the processed data by the motor software.
Software Configuration of Hardware Interface
The SSI hardware interface on the Geo PMAC is software configurable. The configuration is done by
assigning values to several I-variables.
assigning values to several I-variables.
SSI Clock Frequency
The SSI clock frequency, or bit rate, for both channels, is set by variable I1015. The following table
shows the possible values of I1015 and the frequencies they select:
shows the possible values of I1015 and the frequencies they select:
I1015
SSI Clock Freq.
0 153.6
kHz
1 307.2
kHz
2 614.4
kHz
3 1.2288
MHz
The highest frequency that does not exceed the capabilities of the sensor or the cabling should be selected.
Expected Data Format
The Geo PMAC can accept SSI data either in numeric binary format or in Gray code format, as selected
by I1016 for Channel 1 and I1018 for Channel 2. The variable should be set to 2 for numeric binary, or to
3 for Gray code. If Gray code is selected, the Geo PMAC interface hardware will automatically convert
the incoming data to numeric binary before latching it into a register for software access.
by I1016 for Channel 1 and I1018 for Channel 2. The variable should be set to 2 for numeric binary, or to
3 for Gray code. If Gray code is selected, the Geo PMAC interface hardware will automatically convert
the incoming data to numeric binary before latching it into a register for software access.
Word Length
The Geo PMAC interface hardware can be set up to clock in SSI words of 12, 16, 20, or 24 bits, as
selected by I1017 for Channel 1 and I1019 for Channel 2. The following table shows that possible values
of these variables and the word lengths they select:
selected by I1017 for Channel 1 and I1019 for Channel 2. The following table shows that possible values
of these variables and the word lengths they select:
I1017, I1019
Word Length
0 12
bits
1 16
bits
2 20
bits
3 24
bits
If your SSI word length is not one of these lengths, select the next highest length from this table. Then
recognize that the data will be shifted up “too far”, so that the least significant bit (LSB) of the sensor will
not end up in bit 0 of the latching register, and will not be treated as one “count” by the PMAC software.
For example, if you have a 15-bit sensor, you should select the 16-bit word length by setting I1017 or
I1019 to1. Since the 15-bit data will be shifted one bit too far, the LSB from the sensor will appear in bit
1 of the resulting register, and be treated as 2 “counts” by PMAC.
Note:
I1015, I1016, I1017, I1018 and I1019 are only used with the Geo PMAC.