Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Synchronizing Turbo PMAC to External Events
357
•
Set I8 to 0, which forces a real time interrupt every servo cycle. If not running a PLC 0, leave this at
zero permanently.
zero permanently.
•
Begin your programs using R<CR> if @@ has been issued as in the simple case or use <CTRL-R>,
which is the global run command.
which is the global run command.
•
To run a PLC 0, set I8 back to its original value, usually 2. Leaving I8 at 0 probably will cause PLC
0 to starve the background tasks for processor time, causing loss of communications or even a
watchdog timer failure.
0 to starve the background tasks for processor time, causing loss of communications or even a
watchdog timer failure.
•
Enable the PLC programs required. Have the first line of each motion program enable the PLC
programs for its respective Turbo PMAC card.
programs for its respective Turbo PMAC card.
Example:
OPEN PROG 1 CLEAR
ENA PLC 1..31
TM 1000
.
Hardware Position-Capture Functions
The hardware position-capture function latches the current encoder position at the time of an external
event into a special register. It is executed totally in hardware, without the need for software intervention
(although it is set up, and later serviced, in software). This means that the only delays in the capture are
the hardware gate delays (negligible in any mechanical system), so this provides an incredibly accurate
capture function. The accuracy is not limited by the servo update rate, as the position can be captured at
any time during the servo cycle.
Turbo PMAC has high-level move-until-trigger constructs that can utilize the hardware position-capture
function to end a commanded move automatically at a precise distance from the captured feedback trigger
position. The triggered time base slaving function uses the hardware-capture function on the master
position data to provide a precise starting reference point for the following. It is also possible to create
your own low-level algorithms to use the hardware capture functions for other purposes.
event into a special register. It is executed totally in hardware, without the need for software intervention
(although it is set up, and later serviced, in software). This means that the only delays in the capture are
the hardware gate delays (negligible in any mechanical system), so this provides an incredibly accurate
capture function. The accuracy is not limited by the servo update rate, as the position can be captured at
any time during the servo cycle.
Turbo PMAC has high-level move-until-trigger constructs that can utilize the hardware position-capture
function to end a commanded move automatically at a precise distance from the captured feedback trigger
position. The triggered time base slaving function uses the hardware-capture function on the master
position data to provide a precise starting reference point for the following. It is also possible to create
your own low-level algorithms to use the hardware capture functions for other purposes.
Requirements for Hardware Capture
The hardware position-capture function in a Turbo PMAC Servo IC latches the encoder counter value
upon a pre-defined change in a flag and/or index-channel input for that channel. Note that for position
data to have this hardware-capture capability, it must be processed through the encoder counter of a Servo
IC (although the sensor does not have to be an encoder – many resolver-to-digital converters produce
simulated quadrature whose count can be captured this way). Parallel-format and analog feedback do not
support this immediate hardware capture (the closest they can get is to the nearest servo cycle).
upon a pre-defined change in a flag and/or index-channel input for that channel. Note that for position
data to have this hardware-capture capability, it must be processed through the encoder counter of a Servo
IC (although the sensor does not have to be an encoder – many resolver-to-digital converters produce
simulated quadrature whose count can be captured this way). Parallel-format and analog feedback do not
support this immediate hardware capture (the closest they can get is to the nearest servo cycle).
Both PMAC-style and PMAC2-style Servo ICs support the hardware position capture function. The
newest revisions (“D” rev and later) of the PMAC2-style Servo ICs optionally can support capture of
estimated sub-count position as well.
newest revisions (“D” rev and later) of the PMAC2-style Servo ICs optionally can support capture of
estimated sub-count position as well.
The position counter for a given encoder channel can be captured only by using input signals for that
channel. To capture multiple positions simultaneously, wire the triggering signal into inputs for each of
the channels whose position to capture.
channel. To capture multiple positions simultaneously, wire the triggering signal into inputs for each of
the channels whose position to capture.
Setting the Trigger Condition
For both automatic and manual uses, variables I7mn2 and I7mn3 determine what the trigger condition for
the capture is. This is true for both PMAC-style and PMAC2-style Servo ICs. I7mn2 specifies that the
encoder’s index channel is used to trigger, or an input flag for the channel is used, or both; and which
edges of these signals will cause the trigger. I7mn3 specifies which of the four main input flags for the
channel is used for triggering (if I7mn2 specifies that a flag is used).
the capture is. This is true for both PMAC-style and PMAC2-style Servo ICs. I7mn2 specifies that the
encoder’s index channel is used to trigger, or an input flag for the channel is used, or both; and which
edges of these signals will cause the trigger. I7mn3 specifies which of the four main input flags for the
channel is used for triggering (if I7mn2 specifies that a flag is used).