Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 240
encoder conversion table. For example, to use the result of the fourth line of the conversion table as a
source, this I-variable would be $403504.
The second setup line (I-variable) is the “time-base scale factor” which multiplies the differentiated
source value. The final result value equals 2 * Time-Base-Scale-Factor * (New Source Value - Old
Source Value).
Typically, New Source Value and Old Source Value (stored from the previous servo cycle) are in units of
1/32 of a count, the usual scaling of a 1/T encoder conversion result.
When this time base entry is used to calculate a frequency-based time base for a coordinate system, the
TBSF should be set to 2
17
/Real-Time Input Frequency (131,072/RTIF), where the Real-Time Input
Frequency (RTIF) in counts per millisecond, is the frequency at which motion trajectories using this time
base will execute at the programmed speed or in the programmed time. The motion sequence to be slaved
to this frequency should be written assuming that the master is always generating this real-time input
frequency (so always moving at the real-time speed). The true speed of trajectories using this time base
will vary proportionately with the actual input frequency.
Example:
The application requires the use of Encoder 4 on board a Turbo PMAC2 as an untriggered time-base
master for Coordinate System 1. The real-time input frequency is selected as 256 counts/msec. The
conversion table starts with eight single-line entries in I8000 – I8007, with the 4
th
line (I8003) doing a 1/T
conversion of Encoder 4.
Setup On-line Commands
I8003=$078018 ; 1/T conversion of Encoder 4
I8008=$403504 ; Unriggered time base from 1/T encoder
I8009=512 ; TBSF=131072/256
I5193=@I8009 ; C.S.1 use I8009 result for time base
Triggered Time Base ($9, $A, $B): A triggered time-base entry is like a regular untriggered time-base
entry, except that it is easy to freeze the time base, then start it exactly on receipt of a trigger that captures
the starting master position or time.
In a triggered time-base entry, the first setup line (I-variable) contains a 9 A or B in the method digit (bits
20 – 23), depending on its present state. It contains the address of the source register in bits 0 – 18. The
source register for triggered time base must be the starting (X) address for one of the machine interface
channels of a Servo IC. The bit 19 mode switch must be set to 0 if a PMAC-style Servo IC (DSPGATE)
is addressed; it must be set to 1 if a PMAC2-style Servo or MACRO IC (DSPGATE1 or DSPGATE2) is
addressed. Note that setting bit 19 to 1 changes the second hex digit of the I-variable from 7 to F.
The second setup line (I-variable) is the time-base scale factor which multiplies the differentiated source
value. The final result value (when running) equals 512 * Time-Base-Scale-Factor * (New Source Count
- Old Source Count). New Source Count and Old Source Count are the values of the addressed encoder
counter, in counts.
When this time-base entry is used to calculate a frequency-based time base for a coordinate system, the
TBSF should be set to 2
14
/Real-Time Input Frequency (16,384/RTIF), where the Real-Time Input
Frequency (RTIF) in counts per millisecond, is the frequency at which motion trajectories using this time
base will execute at the programmed speed or in the programmed time. (Note that the TBSF is 1/8 of the
value for an untriggered time base, because the triggered time base creates an extra 3 bits [8x] of
fractional information with its 1/T extension.) The motion sequence to be slaved to this frequency should
be written assuming that the master is always generating this real-time input frequency (so always moving
at the real-time speed). The true speed of trajectories using this time base will vary proportionately with
the actual input frequency.