User's Manual

Turbo PMAC User Manual

Motor Compensation Tables and Constants 141

Servo

Interrupts

PMAC 1/T Extension

Velocity Estimation : V =

Position Estimation : P = Counter +/-

Note:

For PMAC2-style Servo ICs of Revision D or newer (introduced 2002), IC-

channel variable I7mn9 must be set to the default value of 0 so the two timers can

be read. (Backward compatibility is maintained.)

Examples:

I8000=$078000 ; Software 1/T extension of Servo IC 0 Channel 1

I8001=$078004 ; Software 1/T extension of Servo IC 0 Channel 2 (PMAC1)

Hardware 1/T Extension (Method digit $C, mode-switch bit 1)

This method lets the Servo IC compute the fractional count value in its hardware. It requires PMAC2-

style Servo ICs of Revision “D” or newer (introduced 2002), with IC-channel variable I7mn9 set to 1 to

enable the hardware calculations.

This method permits new hardware position-capture and position-compare circuits with sub-count

resolution to be used with digital quadrature encoders. It also saves a small amount of computational

time.

Examples:

I8000=$CF8000 ; Hardware 1/T extension of Servo IC 0 Channel 1

I8001=$CF8008 ; Hardware 1/T extension of Servo IC 0 Channel 2 (PMAC2)

No Extension (Method digit $C, mode-switch bit 0)

This method computes no fractional count value, leaving the 5 fractional bits at 0, and just using the

hardware counter for the whole count values. This is primarily used for the simulated feedback from the

pulse-and-direction output for open-loop stepper control, in which the fractional count estimation can

cause unwelcome dithering.