Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
170
Motor Compensation Tables and Constants
Computational Features
The Open Servo provides powerful computational features to permit easy writing of sophisticated and
flexible algorithms.
flexible algorithms.
Access to Turbo PMAC Variables
Open Servo algorithms can utilize all of Turbo PMAC’s I, P, Q, and M-variables, reading and writing to
them as appropriate. As in other user programs, it uses floating-point arithmetic to process these variable
values, even those that are stored as fixed-point values (see Floating-Point vs. Fixed-Point Mathematics,
below). Q-variables are accessed from Open Servo algorithms according to the Coordinate System 1
addressing scheme, no matter which coordinate system the motor executing the Open Servo algorithm is
assigned to.
Open Servo algorithms can utilize all of Turbo PMAC’s I, P, Q, and M-variables, reading and writing to
them as appropriate. As in other user programs, it uses floating-point arithmetic to process these variable
values, even those that are stored as fixed-point values (see Floating-Point vs. Fixed-Point Mathematics,
below). Q-variables are accessed from Open Servo algorithms according to the Coordinate System 1
addressing scheme, no matter which coordinate system the motor executing the Open Servo algorithm is
assigned to.
Compiler-Assigned Pointer Variables
For direct and efficient access to Turbo PMAC registers, Open Servo algorithms support two types of
pointer variables for which the register assignment is made at compilation time, not at program execution
time.
For direct and efficient access to Turbo PMAC registers, Open Servo algorithms support two types of
pointer variables for which the register assignment is made at compilation time, not at program execution
time.
L-variables are pointers to short (24-bit) registers, treated as integer (fixed-point) values. These work in
the same way as L-variables do in compiled PLC programs. They can access either X or Y short
registers, either as entire 24-bit registers (treated as signed integers only), or as portions of the registers 1,
4, 8, 12, 16, or 20 bits wide (treated as signed or unsigned integers, except for 1-bit variables, which are
unsigned only).
the same way as L-variables do in compiled PLC programs. They can access either X or Y short
registers, either as entire 24-bit registers (treated as signed integers only), or as portions of the registers 1,
4, 8, 12, 16, or 20 bits wide (treated as signed or unsigned integers, except for 1-bit variables, which are
unsigned only).
F-variables are pointers to long (48-bit) registers. If the F-variable definition is an L format (e.g. F1-
>L:$10F0), the register is accessed as a 48-bit floating-point register. If the F-variable definition is a D
format variable (e.g. F2->D:$88), the register is accessed as a 48-bit signed integer, but conversion to
or from Turbo PMAC’s 48-bit floating-point format is performed automatically, so it can be used in
floating-point mathematics.
>L:$10F0), the register is accessed as a 48-bit floating-point register. If the F-variable definition is a D
format variable (e.g. F2->D:$88), the register is accessed as a 48-bit signed integer, but conversion to
or from Turbo PMAC’s 48-bit floating-point format is performed automatically, so it can be used in
floating-point mathematics.
Note:
Do not confuse L-variables, which are short-word compiler pointers, with L-format
F-variables and M-variables, which are long-word variables.
F-variables and M-variables, which are long-word variables.
Turbo PMAC itself cannot recognize L-variables or F-variables; these variables have meaning only to the
compiler on the host computer.
compiler on the host computer.
By contrast, when using Turbo PMAC’s M-variable pointers, the register assignment is made when the
line is executed, each time it is executed. This assignment requires about 600 nanoseconds additional
computation time (on a 100 MHz CPU) each time the variable is accessed. However, this does permit the
M-variable definition to be changed during execution, enabling techniques such as indirect addressing.
line is executed, each time it is executed. This assignment requires about 600 nanoseconds additional
computation time (on a 100 MHz CPU) each time the variable is accessed. However, this does permit the
M-variable definition to be changed during execution, enabling techniques such as indirect addressing.
It is possible to use L-variables for fast integer arithmetic while retaining the run-time flexibility of M-
variable definitions, but this adds the run-time definition-access computational penalty described above.
Instead of directly defining L-variables to registers for the compiler, you can reference a range of L-
variables to Turbo PMAC M-variable definitions with the LMOVERLAY {start},{end} compiler
directive. This directive must precede the actual Open Servo program. For example, LMOVERLAY
10,20 instructs the compiler that the definitions of L10 through L20 are to be assigned at run time using
the definitions of M10 through M20 respectively at the time each statement is executed, not at
compilation time.
variable definitions, but this adds the run-time definition-access computational penalty described above.
Instead of directly defining L-variables to registers for the compiler, you can reference a range of L-
variables to Turbo PMAC M-variable definitions with the LMOVERLAY {start},{end} compiler
directive. This directive must precede the actual Open Servo program. For example, LMOVERLAY
10,20 instructs the compiler that the definitions of L10 through L20 are to be assigned at run time using
the definitions of M10 through M20 respectively at the time each statement is executed, not at
compilation time.
Using the M-variable definition and accessing this definition at run time permits indirect addressing
techniques through real-time modification of this M-variable definition using another pointer variable.
techniques through real-time modification of this M-variable definition using another pointer variable.