Tormach PCNC 770 - Page 132

Chapter 7
132
UM10350_PCNC770_Manual_0916A
Programming
There are several types of parameters of dierent purpose and appearance. The only value type
supported by parameters is oang-point; there are no string, Boolean or integer types in G-code
like in other programming languages. However, logic expressions can be formulated with Boolean
operators (AND, OR, XOR, and the comparison operators EQ, NE, GT, GE ,LT, LE), and the MOD,
ROUND, FUP and FIX operators support integer arithmec.
Parameter Syntax
There are three types of parameters, numbered, named local, and named global. The type of the
parameter is dened by its syntax:
numbered - #4711
named local - #<localvalue>
named global - #<_globalvalue>
Parameter Scope
The scope of a parameter is either global or local within a subroune. The scope of each parameter
is inferred from its syntax. Subroune parameters and named local parameters have local scope.
Named global parameters and all numbered parameters starng from #31 are global in scope.
RS274/NGC uses lexical scoping. In a subroune, only the local parameters dened therein and any
global parameters are visible. The local parameters of a calling procedure are not visible in a called
procedure.
Behavior of Uninialized Parameters
Uninialized global parameters and unused subroune parameters return the value zero when used
in an expression. Uninialized named parameters signal an error when used in an expression.
Parameter Mode
The mode of a parameter can either be read/write or read-only. Read/write parameters may be
assigned values within an assignment statement. Read-only parameters cannot be assigned values.
They may appear in expressions, but not on the le-hand side of an assignment statement.
Persistence and Volality
Parameters can either be persistent or volale. When the operang system is powered o, volale
parameters lose their values and are reset to zero. The values of persistent parameters are saved in
a disc le and restored to their previous values when the operang system is powered on again. All
parameters except numbered parameters in the current persistent range (5163 to 5390) are volale.