Delta Tau: Ultralite Programmable Multi-Axis Controller (PMAC2-PC)
The PMAC2-PC and PMAC2-Lite provide state-of-the-art motion control for a wide variety of applications, including machine tools, robotics, semiconductor manufacturing, packaging equipment, and general-purpose automation. They utilize the latest developments in electronics, software, and modern control theory to bring motion control capabilities to a completely new level. The PMAC2-PC and PMAC2-Lite are designed as ISAbus expansion cards, but are capable of standalone operation. The configurations are:
PMAC2-PC: ISAbus-compatible, 1-1/2 slots, 4 or 8 machine interface channels.
PMAC2-Lite: ISAbus-compatible, 1 slot, 4 machine interface channels.
PMAC2-PC and PMAC2-Lite support a wide variety of servo and stepper interfaces:
Analog +/-10V velocity command (requires ACC-8E or equivalent)
Analog +/-10V torque command (requires ACC-8E or equivalent)
Sinusoidal analog +/-10V phase current commands (requires ACC-8E or equivalent)
Direct digital pulse-width modulated (PWM) phase voltage commands (requires ACC-8F, -8K or equivalent)
Pulse-and-direction commands (requires ACC-8S or equivalent)
MACROTM ring network commands (requires ACC-42)
PMAC2-PC and PMAC2-Lite also provide unparalleled speeds and resolutions:
40 MHz encoder count rate
18-bit analog outputs
18 microsecond per axis servo update time (60 MHz)
120 MHz PWM clock frequency (10-bit resolution at 120 kHz, 12-bit and 30 kHz, 14-bit at 7.5 kHz)
120 MHz MLDT (e.g. TemposonicsTM) timer frequency (0.024mm, 0.9mil resolution)
10 MHz maximum pulse-and-direction output frequency
10 MHz maximum position-compare output update rate
125 Mbit/sec optical ring network data rate PMAC2
Delta Tau has designed its own custom application-specific integrated circuits (ASICs) for the PMAC2PC and PMAC2-Lite using the latest sub-micron gate-array technology. Each ASIC contains 45,000 active logic gates. These ASICs contain all of the digital interface circuitry to tie the DSP to the machine; the rest of the circuitry on the board is buffer circuitry.
The DSPGATE1 ASIC contains the digital servo interface circuitry for 4 channels, usually sufficient for four axes of control. Each channel contains:
Three command output sets:
1. Top-and-bottom PWM or serial DAC data with clock
2. Top-and-bottom PWM or serial DAC data with strobe
3. Top-and-bottom PWM or PFM pulse-and-direction
Encoder quadrature or pulse-and-direction decode and count
Index channel input internally gated to 1 quadrature statewide
Four flags with capability to perform hardware latching of encoder position
HOME, PLIM, MLIM, USER
Double-sided position-compare output with auto-increment capability
Amplifier enable output
Amplifier fault input
Four supplementary flag inputs (T, U, V, W)
Two inputs from serial analog-to-digital converters (ADCs)
ADC clock and strobe signal outputs
The DSPGATE1 ASIC also generates several clock frequencies necessary for hardware and software operation, under the userâs software control:
PWM output frequency
DAC clock frequency
Phase interrupt clock frequency and Servo interrupt clock frequency are generated from the first DSPGATE1 only.
ADC clock frequency
Encoder sample clock frequency
Pulse-frequency modulation (PFM) clock frequency
Phase interrupt clock frequency
Servo interrupt clock frequency
There is also a DSPGATE2 ASIC on PMAC2-PC and PMAC2-Lite, which is used for interface to other I/O. The DSPGATE2 ASIC has 3 parts:
General-purpose digital I/O: 56 I/O points for JIO, JTHW, and JDISP ports
Servo interface circuitry for 2 supplemental channels with clock generation
MACRO ring interface circuitry
The general-purpose I/O and the servo interface circuitry on the DSPGATE2 generally share pins, except for two 2-channel encoder inputs and two PWM/PFM output sub-channels. Usually, the shared pins are used for general-purpose I/O instead of extra servo interface circuitry, but this is up to the individual user.
A PMAC2-PC can have one or two DSPGATE1 ASICs; the first one is standard, and the second one comes if Option 1 is ordered. Each also has a DSPGATE2 ASIC supporting the non-servo I/O.
A PMAC2-Lite board (PC bus only) has a single DSPGATE1 ASIC on-board, supporting up to four axes of servo interfaces. It also has a DSPGATE2 ASIC supporting the non-servo I/O. It cannot be expanded on-board to add a second DSPGATE1 ASIC to support full eight axes.
PMAC2-PC Board Configuration
Jumpers on the PMAC2-PC determine the frequency at which the DSP on the PV CPU board will operate. The 56002 DSP has a phased-locked loop (PLL) that allows it to multiply the crystal frequency by a programmable integer value, permitting very high CPU frequencies with a moderate crystal frequency. The crystal frequency on the PV CPU board is always 19.6608 MHz, commonly called 20 MHz.
The component rating of the DSP IC specifies the highest frequency at which it safely can run, but it is the multiplication factor typically set by jumpers that specifies the frequency at which it actually runs. Usually this is a frequency at or near the maximum for the component.
It is safe to run a DSP at a frequency below the maximum. It may be possible to run a DSP at a frequency higher than its maximum frequency, particularly at low ambient temperatures, but safe operation cannot be guaranteed. Unpredictable and possibly dangerous operation may result.
On power-up/reset, the DSP, operating at the crystal frequency of 20 MHz, reads the frequency jumpers (E2 and E4) and writes into its own PLL multiplier register at X:$FFFD. Bits 0-3 of this word contain a value one less than the multiplier value (if the frequency is being multiplied by 3, these bits contain a value of 2).
To check the value of the multiplier, use the RHX:$FFFD on-line command and look at the last hexadecimal digit. The actual multiplier is one greater than the value in this last digit. Alternately, define an M-variable such as M99->X:$FFFD,0,4 and then read from or write to these bits with the M-variable.