Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
338
Writing and Executing Motion Programs
Staying Ahead of Executing Line
The key to the handling of a rotary program buffer is knowing how many lines ahead it is; that is, how
many program lines have been loaded ahead of the program line that PMAC is executing. Typically it
will load ahead until a certain number of lines ahead is reached, and then wait until the program catches
up to within a smaller number of lines ahead. A real-time application may just work one line ahead of the
executing line; an application doing periodic downloading of a huge file may get 1000 lines ahead, and
then start again when the program has caught up to within 500 lines.
many program lines have been loaded ahead of the program line that PMAC is executing. Typically it
will load ahead until a certain number of lines ahead is reached, and then wait until the program catches
up to within a smaller number of lines ahead. A real-time application may just work one line ahead of the
executing line; an application doing periodic downloading of a huge file may get 1000 lines ahead, and
then start again when the program has caught up to within 500 lines.
PR Command
There are several ways of telling how far ahead it is. First is the PR (program remaining) command,
which returns the number of lines ahead. This provides a very simple polling scheme, but one that is
probably not good for tight real- time applications.
which returns the number of lines ahead. This provides a very simple polling scheme, but one that is
probably not good for tight real- time applications.
BREQ Interrupt
For tightly coupled applications, there are hardware lines to handle the handshaking for the rotary buffer,
and variables to control the transition points of the lines. The BREQ (Buffer Request) line goes high
when the rotary buffer for the addressed coordinate system wants more program lines, and it goes low
when it does not. This line is wired into PMAC-PC’s programmable interrupt controller, so it can be used
to generate an interrupt to the host PC. (See Using the PMAC-PC to Interrupt the Host PCof this
manual.) The complement, BREQ/, is provided on the JPAN connector. In addition, there is a Buffer
Full (BREQ/) status bit for each coordinate system.
and variables to control the transition points of the lines. The BREQ (Buffer Request) line goes high
when the rotary buffer for the addressed coordinate system wants more program lines, and it goes low
when it does not. This line is wired into PMAC-PC’s programmable interrupt controller, so it can be used
to generate an interrupt to the host PC. (See Using the PMAC-PC to Interrupt the Host PCof this
manual.) The complement, BREQ/, is provided on the JPAN connector. In addition, there is a Buffer
Full (BREQ/) status bit for each coordinate system.
I17 Stops Interrupts
Variable I17 controls how many lines ahead the host can load and still get BREQ true. If a program line
is sent to a rotary buffer, BREQ is taken low, at least temporarily. If still less than I17 lines ahead of the
executing line, BREQ is taken high again, which can generate an interrupt. If it is I17 or more lines
ahead, BREQ is left low. When a rotary program buffer is entered with OPEN ROT or the addressed
coordinate system is changed, BREQ is taken low, and then set high if the buffer is less than I17 lines
ahead of the executing point.
Variable I17 controls how many lines ahead the host can load and still get BREQ true. If a program line
is sent to a rotary buffer, BREQ is taken low, at least temporarily. If still less than I17 lines ahead of the
executing line, BREQ is taken high again, which can generate an interrupt. If it is I17 or more lines
ahead, BREQ is left low. When a rotary program buffer is entered with OPEN ROT or the addressed
coordinate system is changed, BREQ is taken low, and then set high if the buffer is less than I17 lines
ahead of the executing point.
I16 Restarts Interrupts
Variable I16 controls where BREQ gets set again as the executing program in the rotary buffer catches up
to the last loaded lines. If after execution of a line, there are less than I16 lines ahead in the rotary buffer,
BREQ is set high. This can be used to signal the host that more program lines need to be sent.
Variable I16 controls where BREQ gets set again as the executing program in the rotary buffer catches up
to the last loaded lines. If after execution of a line, there are less than I16 lines ahead in the rotary buffer,
BREQ is set high. This can be used to signal the host that more program lines need to be sent.
By using these two variables and the BREQ line for interrupts, an extremely fast and efficient system can
be created for downloading programs in real time from the PC.
be created for downloading programs in real time from the PC.
If the Buffer Runs Out
If the program calculation catches up with the load point of the rotary buffer, there is no error; program
operation will suspend until more lines are entered into the rotary buffer. Technically, the program is still
running; a Q or A command must be given to truly stop the program.
If PMAC is in segmentation mode (I13>0) and is executing the last line in the rotary buffer, as long as a
new line is entered before the start of deceleration to stop, PMAC will blend into the new move without
stopping.
If the program calculation catches up with the load point of the rotary buffer, there is no error; program
operation will suspend until more lines are entered into the rotary buffer. Technically, the program is still
running; a Q or A command must be given to truly stop the program.
If PMAC is in segmentation mode (I13>0) and is executing the last line in the rotary buffer, as long as a
new line is entered before the start of deceleration to stop, PMAC will blend into the new move without
stopping.
Closing and Deleting Buffers
The CLOSE command closes the rotary buffers just as it does for other types of buffers. Closing the
rotary buffers does not affect the execution of the buffer programs; it just prevents new buffered
commands from being entered into the buffers until they are reopened.
rotary buffers does not affect the execution of the buffer programs; it just prevents new buffered
commands from being entered into the buffers until they are reopened.
DELETE ROT erases the rotary buffer for the addressed coordinate system and de-allocates the memory
that had been reserved for it.
that had been reserved for it.