Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
58
Setting Up Feedback and Master Position Sensors
In addition, the direction sense of the whole-count data must match that of the fractional-count data. For
the low-resolution interpolators, this requires that the decode variable be set to 7. If this value does not
produce the direction sense needed, change the wiring of the encoder into the accessory (exchange sine
and cosine signals, or the plus and minus lines of one channel).
the low-resolution interpolators, this requires that the decode variable be set to 7. If this value does not
produce the direction sense needed, change the wiring of the encoder into the accessory (exchange sine
and cosine signals, or the plus and minus lines of one channel).
For the high-resolution interpolators, the conversion table will check the direction sense of the encoder
decode at power-up/reset and adjust the direction sense of the fractional data accordingly. This permits
the setting of the direction sense as needed by setting the decode variable to 3 or 7, but if this variable
setting is changed, save the setting and reset the card before the fractional direction sense matches.
decode at power-up/reset and adjust the direction sense of the fractional data accordingly. This permits
the setting of the direction sense as needed by setting the decode variable to 3 or 7, but if this variable
setting is changed, save the setting and reset the card before the fractional direction sense matches.
Encoder Filter Bypass: I7mn1 (PMAC-style ICs)
If a low-resolution interpolator is connected to a PMAC-style Servo IC, the encoder’s digital delay filter
must be bypassed for both the channel with the encoder signal, and the channel with the flags, in order to
keep the whole-count and fractional-count data properly synchronized. The same is true if using the Acc-
51P high-resolution interpolator with its own PMAC-style Servo IC on board. Bypassing the delay filter
is selected by setting channel variable I7mn1 to 1.
must be bypassed for both the channel with the encoder signal, and the channel with the flags, in order to
keep the whole-count and fractional-count data properly synchronized. The same is true if using the Acc-
51P high-resolution interpolator with its own PMAC-style Servo IC on board. Bypassing the delay filter
is selected by setting channel variable I7mn1 to 1.
Conversion Table Processing Setup – Turbo PMAC Interface
Sinusoidal encoders wired into a high-resolution (x4096) Acc-51x interpolator connected to a Turbo
PMAC are processed in the Turbo PMAC’s conversion table by a hi-res interpolator entry (method digit
$F), in which the fractional-count data is computed mathematically from the readings of the sine and
cosine A/D converters. The least significant bit (LSB) of the result represents 1/4096 of an encoder line.
PMAC are processed in the Turbo PMAC’s conversion table by a hi-res interpolator entry (method digit
$F), in which the fractional-count data is computed mathematically from the readings of the sine and
cosine A/D converters. The least significant bit (LSB) of the result represents 1/4096 of an encoder line.
Encoder Interpolation: High Resolution
Analog “SIN / COS” Encoders
+
-
SIN / COS
Signals
A
B
A
B
n-bit
A/D
Differential
Amplifier
+
-
Analog
Photo
Current
Encoder
Controller
n-bit
A/D
Decoder/
Counter
Comparator
“1 bit A/D”
Address
Data
Sinusoidal encoders wired into a low-resolution (x128/x256) interpolator connected to a Turbo PMAC are
processed in the Turbo PMACs conversion table by a parallel extension of incremental encoder entry
(method digit $C), in which the fractional-count data has been computed externally in the interpolator’s
look-up table and is just appended to the whole count data by the conversion table. The LSB of the result
represents 1/128 or 1/256 of an encoder line, depending on the setting of the resolution jumper on the
interpolator.
processed in the Turbo PMACs conversion table by a parallel extension of incremental encoder entry
(method digit $C), in which the fractional-count data has been computed externally in the interpolator’s
look-up table and is just appended to the whole count data by the conversion table. The LSB of the result
represents 1/128 or 1/256 of an encoder line, depending on the setting of the resolution jumper on the
interpolator.