PMAC Product Guide Termination Resistors The PMAC-Lite provides sockets for termination resistors on differential input pairs coming into the board. As shipped, there are no resistor packs in these sockets. If these signals are brought long distances into the PMAC-Lite board and ringing at signal transitions is a problem, 6-pin SIP resistor packs may be mounted in these sockets to reduce or eliminate the ringing. All termination resistor packs are the type that has independent resistors (no common connection) with each resistor using two adjacent pins. The following table shows which packs are used to terminate each input device:
DAC Output Signals If PMAC is not performing the commutation for the motor, only one analog output channel is required to command the motor. This output channel can be either single-ended or differential, depending on what the amplifier is expecting. For a single-ended command using PMAC channel 1, connect DAC1 (pin 43) to the command input on the amplifier. Connect the amplifier’s command signal return line to PMAC’s AGND line (pin 58). In this setup, leave the DAC1/ pin floating; do not ground it. For a differential command using PMAC channel 1, connect DAC1 (pin 43) to the plus command input on the amplifier. Connect DAC1/ (pin 45) to the minus-command input on the amplifier.
PMAC’s AGND should still be connected to the amplifier common. If the amplifier is expecting separate sign and magnitude signals, connect DAC1 (pin 43) to the magnitude input. Connect AENA1/DIR1 (pin 47) to the sign (direction input). Amplifier signal returns should be connected to AGND (pin 58). This format requires some parameter changes on PMAC (see Ix25 and Ix02). Jumper E17 controls the polarity of the direction output; this may have to be changed during the polarity test.
This magnitude-and-direction mode is suited for driving servo amplifiers that expect this type of input, and for driving voltage-to-frequency (V/F) converters, such as PMAC's ACC-8D Option 2 board, for running stepper motor drivers. To limit the range of each signal to +/- 5V, use parameter Ix69. Any analog output not used for dedicated servo purposes may be utilized as a general-purpose analog output. Usually, this is done by defining an M-Variable to the digital-to-analog-converter register (suggested M-Variable definitions M102, M202, etc.), and then writing values to the M-Variable. The analog outputs are intended to drive high-impedance inputs with no significant current draw.
The 220 Ω output resistors will keep the current draw lower than 50 mA in all cases and prevent damage to the output circuitry, but any current draw above 10 mA can result in noticeable signal distortion. Example: 30 Machine Connections Device Resistor Pack Device Resistor Pack Encoder 1 RP51 Encoder 3 RP53 Encoder 2 RP52 Encoder 4 RP54