Delta Tau GEO BRICK LV User Manual

T

1

T

2

T

1

T

2

A

B

Servo

Interrupts

Velocity Estimation :  V   =

K

n

Position Estimation :  P   = Counter +/-

T

2

T

1

n

T

1

 

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.) 

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.