User's Manual

PMAC User Manual

56 Setting Up a Motor

Note:

When using dual feedback, the motor flags specified by Ix25 (see below) should

have the same number as the position-loop encoder. Otherwise, the hardware

position-capture function for homing will not work, and the less accurate software

position-capture function must be used. For example, if the velocity-loop encoder

is ENC1 (Ix04=$0720) and the position-loop encoder is ENC2 (Ix03=$0721), the

motor flags must be Flags 2 (Ix25=$C004) in order to use the hardware position

capture. If the flags are of a different number, the software position capture

function must be specified for homing by setting bit 16 of Ix03 to 1 (e.g.,

Ix03=$10721).

Selecting the Master Position Source

Variable Ix05 determines from which register Motor x gets its master position information. The value of

Ix05 is the address of the register. Usually, this is a register in the Encoder Conversion Table that

contains processed information from a position sensor. With the default setup of the Encoder Conversion

Table, the default value of Ix05 is the register address of processed data from Encoder 2 (i.e., all motors

use Encoder 2 as a master). This setting permits a single master encoder to be brought in on the control-

panel port (J2), and have any motor follow it if that motor’s following function is enabled.

The master position is the source of data for the PMAC position following function (often called

electronic gearing). This topic is covered in detail in the Synchronizing PMAC to External Events section

of this manual.

Selecting the Flag Register

Variable Ix25 determines which register Motor x uses for its flag inputs (limits, home flag, amplifier

fault, and index channel) and output (amplifier-enable/direction). The value of Ix25 is the address of the

FAULT4, CHC4, and AENA4/DIR4). In order to use the accurate hardware position capture function for

homing, the number of the flag set must match the number of the position-loop encoder specified by Ix03.

Selecting the Power-Up Mode

Variable Ix80 determines whether the motor will be enabled or disabled at the end of the power-up/reset

cycle. If Ix80 is 1, the motor will be enabled automatically at the end of the power-up/reset cycle, in a

closed-loop, zero velocity state, with the commanded position set equal to the actual position at the time.

If a phasing search is required for a PMAC-commutated motor, it will be done automatically. If Ix80 is 0,

the motor will be left disabled (killed). A command will be required to enable the motor: for a PMAC-

commutated motor, the $ command must be used; for a motor not commutated by PMAC, either the $ or

J/ command may be used, or the A command for all the motors in a coordinate system, or the <CTRL-

A> command for all PMAC motors.

Types of Position Sensors

PMAC is designed to take incremental encoder feedback without any accessories. With the appropriate

accessories, it can also take resolver, absolute encoder, analog, or magnetostrictive linear displacement

transducer feedback. These features are explained in further detail below.

Quadrature Encoder Feedback

PMAC can take quadrature encoder signals as position feedback with software programmable decode

selection of x1, x2, or x4 decode (pulse and direction decode is also possible). Encoder I- variable 0

(I900, I905, etc.) determines the decode method and direction sense for each encoder. The 24-bit

hardware counter is software-extended to over 36 bits (64 billion counts). A software parameter (Ix27)

allows position rollover at a user-specified value: this is especially useful for rotary axes. Any unused

encoder counter in a DSPGATE IC may be utilized as a hardware timer (refer to I900 description).