Altera Nios II C2H Compiler - Manual (Page 122)

6–4 9.1 Altera Corporation
Nios II C2H Compiler User Guide November 2009
Interrupt Pragma
Interrupt
Pragma To use a hardware accelerator in interrupt mode, add the following line
to your function source code:
#pragma altera_accelerate \
enable_interrupt_for_function <function name>
At the next software compilation, the C2H Compiler creates a new header
file containing all the macros needed to use the accelerator and service the
interrupts it generates.
This pragma causes the function (which is assumed to be a top-level
accelerated function, not an accelerated subfunction) to be an interrupt-
mode accelerator. Specifically, the following things change:
■ The accelerator's control slave has an IRQ signal, which is asserted
every time the function has completed execution.
■ The polling loop in the generated driver file is removed. When the
function is called, the CPU immediately returns after launching the
accelerator.
■ A header file is generated, providing macros and definitions
required for you to write an ISR. The macros are summarized in
Table 6–1 .
An example of this header file is shown in Example 6–4 for an
accelerated function called coprocess() in a Nios II IDE project
called my_project. The file is generated in <Project Path>/
<Configuration>, where <Project Path> is the software project
directory, and <Configuration> is the project configuration name
(Release or Debug). The file name is ACCELERATOR_<Project
Name>_<Function Name>_IRQ.h, where <Project Name> is the name
of the project (usually the same as <Project Path>), and <Function
Name> is the name of the function you are accelerating.
Table 6–1. C2H Accelerator Interrupt Macros
Purpose Macro Name
Return value ACCELERATOR _ <Project Name> _ <Function Name> _ GET_RETURN_VALUE()
Interrupt clear ACCELERATOR _ <Project Name> _ <Function Name> _ CLEAR_IRQ()
Check status ACCELERATOR _ <Project Name> _ <Function Name> _ BUSY()