Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 245
Reserved Setup Word: The fourth setup line (I-variable) of a tracking filter entry is reserved for future use.
It is not presently used, and can be set to 0.
Filter Integral Gain Word: The fifth setup line (I-variable) of a tracking filter entry contains the filter
integral gain value K
i
, which determines how quickly the integrated error contributes to the filter output.
Each servo cycle, the amount (Ki/2
23
) * Err(n) is added to the integrator and to the filter output.
Result Word: The output value of the tracking filter is placed in the X-register of the fifth line of the
conversion table entry. An operation that uses this value should address this fifth register; for example
Ixx03 for position-loop feedback, or the source address for a time-base conversion-table entry (to keep
position lock in time base, this filter must be executed before the time-base differentiation, not afterward).
Addition/Subtraction of Entries ($E): The $E entry is used to add the results of two other entries in the
Table, possibly after negating one or both of them (which can effectively create subtraction), with the
option of integrating the sum. It is a single-line entry.
Control Digit: The second hex digit of the I-variable consists of four independent control bits (bits 19-16)
and determines whether the result is integrated or not, whether a second source entry is used or not, and
whether each of the source entries is negated before addition or not.
If the bit 19 mode switch bit is 0, which makes the second hex digit 0, the values in the two specified
entries are simply added. If the mode switch bit 19 is 1, the sum of the two entries.
If bit 18 is set to 1, the second entry to be added (as specified by bits 8-15) is not used. This permits easy
negation (change in sign) of a single entry. If bit 18 is set to 0, the second entry is used.
If bit 17 is set to 1, the second entry to be added (as specified by bits 8-15) is negated before the addition,
which means that it is effectively subtracted from the first entry. If bit 17 is not set to 1, the second entry
to be added is not negated.
If bit 16 is set to 1, the first entry to be added (as specified by bits 0-7) is negated before the addition,
which means that it is effectively subtracted. If bit 16 is not set to 1, the first entry to be added is not
negated.
Second Source Offset: Bits 8-15, which form the third and fourth hex digits of the entry, specify the
offset from the beginning of the table to the second entry to be used used, as an unsigned 8-bit quantity.
The value in these digits should equal the number of the I-variable matching the second entry minus 8000.
First Source Offset: Bits 0-7, which form the fifth and sixth hex digits of the entry, specify the address
offset from the beginning of the table to the first entry to be used, as an unsigned 8-bit quantity. The
value in these digits should equal the number of the I-variable matching the first entry minus 8000.
Examples:
To add the results of the first two lines in the table, from I8000 and I8001, the I-variable would be
$E00100. The E specifies addition, the 0 specifies no integration, using the second source, and no
negation of either source. The 01 specifies the second line of the table (matching I8001) as the second
source, and the final 00 specifies the first line of the table (matching I8000) as the first source.
To subtract the result of the second line (from I8001) of the table from that of the first line (from I8000),
the I-variable would be $E20100. The E specifies addition, the 2 (0010 binary) specifies no integration,
using the second source, negating the second source, but not the first source. The 01 specifies the second
line of the table (matching I8001) as the second source, and the final ‘00’ specifies the first line of the
table (matching I8000) as the first source.
To invert the 20
th
line of the table (from I8019), the I-variable would be $E50013. The E specifies
addition, the 5 (0101 binary) specifies no integration, not using the second source, and negating the first
source. The 00 is not important, because the second source is not used. The 13 (19 decimal) specifies the
result matching I8019 as the first source.