User's Manual

PMAC User Manual
Input/Output: Connecting PMAC to the Machine 51
Analog Input
The Wiper analog input (0 to +10V on PMAC PC, -VME, and -STD; -10V to +10V on PMAC Lite,
referenced to digital ground) provides an input to a voltage-to-frequency converter (V/F) with a gain of 25
kHz/Volt, providing a range of 0-250 kHz. The output of the V/F can be connected to the Encoder 4
counter using jumpers E72 and E73. If these jumpers are on, nothing else should be connected to the
Encoder 4 inputs. Make sure that the Encoder 4 jumper E24 is set for single-ended signals, connecting
pins 1 and 2.
Frequency Decode
When used in this fashion, Encoder 4 must be set up for pulse-and-direction decode by setting I915 to 0
or 4. Usually a value of 4 is used, because with CHB4 (direction) unconnected, a positive voltage causes
the counter to count up.
Power Supply
For the V/F converter to work, PMAC must have +/-12V supply referenced to digital ground. If PMAC
is in a bus configuration, this usually comes through the bus connector from the bus power supply. In a
standalone configuration, still this supply must be brought through the bus connector (or the supply
terminal block on the PMAC Lite), or it must be jumpered over from the analog side with E85, E87, and
E88, defeating the optical isolation on the board.
PMAC Lite Special Considerations
Since the PMAC Lite’s Wiper input has bipolar capability, it has a few special considerations. If used in
bipolar fashion, the offset potentiometer (R18) should be adjusted for minimum deadband in the zero
crossing (monitor on CHA4 on the JMACH1 connector). If used in unipolar fashion, R18 should be
adjusted for some deadband to assure that 0V in creates no frequency; also jumper E73 should be left
OFF to make sure no glitches get into the sign bit of the counter.
On PMAC Lite, the pulse and direction signals may be output on the CHA4 and CHB4 pins, respectively,
of the JMACH1 connector. These can be used to command a stepper-motor driver. The DAC4 output
can be wired into the WIPER input, which provides both the feedback that the servo loop requires, and
the command signals to the driver. This permits the PMAC Lite to drive one stepper motor without a
special accessory board.
Software Processing
The encoder conversion table can then take the difference in the counter each servo cycle and scale it,
providing a value proportional to frequency, and therefore to the input voltage. Usually this is used for
feedrate override (time base control), but the resulting value can be used for any purpose. Refer to the
Time-Base Control section in this manual.
Status Outputs
There are five dedicated low-true outputs on the JPAN connector, usually used to light LEDs. They are
BRLD/ (buffer-request LED), IPLD/ (in-position LED), EROR/ (Error condition LED), F1LD/ (1st
warning following error LED), and F2LD/ (which goes true when the watchdog timer trips). BRLD/,
ERLD/, and F2LD/ are global status lines. IPLD/ and F1LD/ are coordinate-system specific status lines.
If I2=0, they refer to the panel-selected coordinate system (by FDPn/). If I2=1, they refer to the host-
selected coordinate system (&n).
If I2=0 but no coordinate system is selected (all FPDn/ inputs are floating or pulled high), these lines can
be used as general purpose outputs, addressed as bits 20-23 of Y:$FFC2 (Y:$FFFD bits 0-3 on PMAC
STD).