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Neuron C Reference Guide 201

Symbol Description

_NCC5 Defined for version 5 of the Neuron C compiler. This

version corresponds to Version 2.2 of the Neuron C

language.

_NEURONC Defined for all versions of the Neuron C compiler.

_NODEBUILDER Defined for the Neuron C compiler that is included with

the NodeBuilder FX Development Tool, and later versions.

_SHORTSTACK Defined for the Neuron C compiler that is included with

the ShortStack LonTalk Interface Developer utility for

model files.

Built-In Semaphore

For Series 5000 chips, you use the Neuron C __lock { } keyword, followed by a

code block, within the application or the interrupt service routine (the interrupt

task) to acquire the built-in binary semaphore and synchronize access to shared

resources. The __lock keyword precedes a block of code (within a pair of curly

braces) that is controlled by the semaphor.

The semaphore is not supported for the lowest system clock rates (5 MHz and 10

MHz).

You can use the __lock keyword within either Neuron C code or pure C code (for

example, within a library).

Example:

interrupt (IO_0) {

... // do something not guarded by the semaphore

__lock { // acquire semaphore

... // do something guarded by the semaphore

} // release semaphore

... // more unguarded code

}

Because there is only one semaphore, you cannot nest locks. Nested locks yield a

compiler error, NCC#585. While the compiler detects and prevents direct nesting

of __lock{ } constructs within the same function, when task, or interrupt task, the

compiler does not detect runtime nesting.

Example: The following example illustrates nesting of locks at runtime.

void f() {

__lock {

... // do something

}

interrupt (IO_0) {

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Echelon Neuron C Bedienungsanleitung Seite 221