User's Manual

PMAC User Manual
74 Setting Up a Motor
Converted Data
The last source data word is stored in the first X word of the entry in the table, and the net result is stored
in the second X word. The value of the net result is 2 * Scale_factor * (New_source - Old_source). To
use this value to control the time-base of a coordinate system, enter this address as the value of Ix93
(Time-Base Source Address) for the coordinate system.
Y - Register
{Scale factor}
HEX
$720
$723
$728
$729
X - Register
Interpolated Cts(n)
Interpolated Cts(n-1)
Result
DEC
1824
1827
1832
1833
$00
{1/T}
C00C
{Enc 4 counter}
$40
{Time Base}
0723
{Int. Enc. 4}
I193 = 1833
Result = 2*S.F * [Interp Cts (n) - Interp Cts (n-1)]
= 2 (2
17
/RTIF) (2
5
* IF * I10/2
23
)
= I10 * (IF/RTIF)
Figure 11 Conversion Table Example for Time-Base Entry
Triggered Time-Base Conversion Entries
For those applications where it is necessary to synchronize exactly to the position of the master encoder,
the conversion table provides the capability to freeze the time-base while calculating the first moves of
the synchronized sequence. Then have the time base start up referenced exactly to the master position
that occurred when the starting trigger occurred (usually the index channel of the master encoder). This
provides a complete position lock of the slave to the master; there is no need for subsequent adjustment to
make sure that they are phased in, as would be the case for normal (untriggered) time-base control.
Entry Format
Unlike the normal (untriggered) time-base conversion, the source address must be that of the encoder
registers in the DSP-GATE with the raw (unprocessed) data. The triggered time-base conversion does the
1/T interpolation itself. The valid addresses for triggered time-base entries are the same as those for the
Incremental Encoder Entries: $C000 for Encoder 1, $C004 for Encoder 2, and so on, to $C03C for
Encoder 16.
Triggered Time-Base Conversion
X-Words
Y-Words
1. Last cycle's source data:
Bits 0-4: Fractional bits
Bits 5-23: Integer Bits
1. Source and process:
Bits 0-15: Address of source (always a set of
DSPGATE encoder registers)
Bits 16-23:
$90 (frozen; for preparation)
$B0 (armed; waiting for trigger)
$A0 (running; post-trigger)
3. Actual time-base value: When running,
the product of scale factor and difference
between last two source values.
2. Time-base scale factor: supplied by user;
equal to 131,072 / real-time-input-frequency
in cts/msec.