Altera Nios II C2H Compiler Uživatelský manuál stáhnout pdf (Strana 63)

Altera Corporation 9.1 3–23

November 2009 Nios II C2H Compiler User Guide

C-to-Hardware Mapping Reference

The write-data signal for the Avalon-MM master port is computed and

registered in parallel with the address assignment. As soon as

ptr_to_int_i_addr and ptr_to_int_i_writedata are valid,

write-enable control logic asserts the signal ptr_to_int_i_write,

which initiates a transfer on the master port.

Figure 3–11 shows the logic created for the following write operation to a

dereferenced pointer. Translation of the data-computation logic follows

the rules described in section “Assignments” on page 3–2.

*(ptr_to_int + i) = a*x + y;

Figure 3–11. Complex Write Operation

Master-Slave Connections

The C2H Compiler uses pragmas that allow user control of master-slave

connections and arbitration shares. This section describes the pragmas to

control master-slave connections.

The C language specification dictates that when a compiler

implementation encounters a pragma directive it does not recognize, the

compiler ignores the pragma. By using pragmas, you can write directives

to optimize the C2H Compiler results, without making the C code

incompatible with other compilers.

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Altera Nios II C2H Compiler Uživatelský manuál Strana 63