TASKING VX-toolset for TriCore用户指南：C语言与数据类型详解

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本资源为《TASKING VX-toolset for TriCore User Guide》手册，适用于MA160-800版本的v6.2r2，发布日期为2018年3月13日。该文档由TASKING BV享有版权，允许个人用户在非商业且不进行复制或网络传播的情况下打印使用。未经TASKING BV明确书面许可，任何形式的机械或电子复制，包括翻译成其他语言，除非用于出版评论中的简短摘录，否则都受到严格限制。未经授权的复制可能根据当地法律也受到禁止，违规者可能会面临刑事和民事处罚。主要内容集中在汽车编程领域，使用的是TASKING的VX-toolset工具集，针对的是TriCore处理器。手册的第一部分是C语言介绍，这是汽车嵌入式系统编程的基础。在C语言章节中，详细讲解了数据类型，其中特别关注了半精度浮点数（Half Precision Floating-Point）。半精度浮点数（Half Precision Floating-Point）是一种在内存占用较少、计算速度较快但精度相对较低的数据类型，适合于对精度要求不高的场合，例如图形处理、信号处理等，尤其在资源受限的嵌入式系统中，如汽车电子系统，它能有效节省存储空间和提高程序执行效率。在使用TASKING VX-toolset时，开发者可以利用这些数据类型来编写优化的代码，实现高效的汽车控制逻辑或者传感器数据处理。手册还可能包含其他内容，如编译器设置、API使用指南、调试技巧、性能优化策略以及针对TriCore处理器特有的特性支持。此外，对于初学者来说，可能会有详细的示例代码和教程，帮助用户逐步掌握如何使用VX-toolset进行汽车编程，并解决在实际项目中可能遇到的问题。这是一份深入浅出的指南，旨在帮助汽车工程师和技术人员利用TASKING VX-toolset高效地开发和维护TriCore处理器上的软件，确保汽车系统的稳定性和性能。无论是对于入门级开发者还是经验丰富的专业人士，都能从中获取宝贵的参考资料。

char h;

char j;

} ST_64;

ST_64 st_64_1;

ST_64 st_64_2;

void main( void )

{

st_64_1 = st_64_2;

}

and use the following invocations:

ctc struct.c -t0

ctc struct.c

With #pragma pack 2 you can disable the LD.D/ST.D structure and union copy optimization to ensure

halfword structure and union packing when possible. This "limited" halfword packing only supports

structures and unions that do not contain double, circular buffer, __laccum or pointer type members and

that are not qualified with #pragma align to get an alignment larger than two bytes. With #pragma

pack 0 you turn off halfword packing again.

#pragma pack 2

typedef struct {

unsigned char uc1;

unsigned int ui1;

unsigned short us1;

unsigned int ui2;

unsigned short us2;

} packed_struct;

#pragma pack 0

When you place a #pragma pack 0 before a structure or union, its alignment will not be changed:

#pragma pack 0

packed_struct pstruct;

The alignment of data sections and stack can affect the alignment of the base address of a halfword

packed structure. A halfword packed structure can be aligned on a halfword boundary or larger. When

located on the stack or at the beginning of a section, the alignment becomes a word, because of the

minimum required alignment of data sections and stack objects. A stack or data section can contain any

type of object. To avoid wrong word alignment of objects in the section, the section base is also word

aligned.

1.1.4. Increasing the Alignment: __align()

By default the TriCore compiler aligns variables and functions to the minimum alignment required by the

architecture. See Section 1.1, Data Types. With the attribute __align() you can increase the alignment

TASKING VX-toolset for TriCore User Guide

Section typesPointer

size

Maximum

object size

LocationDescriptionQualifier

a1data, a1rom,

a1bss

32-bit64 kBSign-extended 16-bit

offset from address

Uninitialized / constant

/ cleared data

__a1

a8data, a8rom,

a8bss

32-bit64 kBSign-extended 16-bit

offset from address

Uninitialized / constant

/ cleared data

__a8

a9data, a9rom,

a9bss

32-bit64 kBSign-extended 16-bit

offset from address

Uninitialized / constant

/ cleared data

__a9

If you do not specify __near or __far, the compiler chooses where to place the declared object.

With the C compiler option --default-near-size (maximum size in bytes for data elements that are

by default located in __near sections) you can specify the size of data objects which the compiler

then by default places in near memory.

All these memory qualifiers (__near, __far, __a0, __a1, __a8 and __a9) are related to the object

being defined, they influence where the object will be located in memory. They are not part of the type of

the object defined. Therefore, you cannot use these qualifiers in typedefs, type casts or for members of

a struct or union.

Address registers A0, A1, A8, and A9 are designated as system global registers. They are not part of

either context partition and are not saved/restored across calls. They can be protected against write

access by user applications. A0, A1, A8 and A9 are freely to use on any type of data.

It is not allowed to assign ROM and RAM data to the same group. With the address registers A0, A1, A8

and A9 you can only access ROM or RAM but not both. Mixed ROM and RAM section types are not

allowed for qualifiers __a0, __a1, __a8 and __a9. When this happens the linker issues the message:

Section .rodata_ax in group ax has memory type ROM but

expected memory type RAM like section .data_ax in the same group

where x is one of 0, 1 ,8, 9.

For example, it is not allowed to have variable a0rom and a0ram in a single application.

__a0 const int a0rom=1;

__a0 int a0ram=1; // Mixing ROM/RAM is not allowed

For this example the linker reports that the section .rodata_a0.a0.a0rom in group a0 has memory

type ROM but expected memory type RAM like section .data_a0.a0.a0ram in the same group.

Examples using memory qualifiers

To declare a fast accessible integer in directly addressable memory:

int __near Var_in_near;

TASKING VX-toolset for TriCore User Guide

1.2.2. Placing an Object at an Absolute Address: __at()

Just like you can declare a variable in a specific part of memory (using memory qualifiers), you can also

place an object or a function at an absolute address in memory.

With the attribute __at() you can specify an absolute address. The address is a 32-bit linear address.

Examples

unsigned char Display[80*24] __at( 0x2000 );

The array Display is placed at address 0x2000. In the generated assembly, an absolute section is

created. On this position space is reserved for the variable Display.

int i __at(0x1000) = 1;

void f(void) __at( 0xa0001000 ) { __nop(); }

The function f is placed at address 0xa0001000.

Restrictions

Take note of the following restrictions if you place a variable at an absolute address:

• The argument of the __at() attribute must be a constant address expression. Otherwise the compiler

generates an error.

• You can place only global variables at absolute addresses. Parameters of functions, or automatic

variables within functions cannot be placed at absolute addresses. If they are, the compiler generates

an error.

• A variable that is declared extern, is not allocated by the compiler in the current module. Hence you

should not use the keyword __at() on an external variable. If you do, the compiler ignores the keyword

__at() without generating an error. Use __at() at the definition of the variable.

• You cannot place structure members at an absolute address. If you do, the compiler ignores the keyword

__at() and generates a warning.

• Absolute variables cannot overlap each other. If you declare two absolute variables at the same address,

the assembler and/or linker issues an error. The compiler does not check this.

1.2.3. Accessing Bits

There are several methods to access single bits in a variable.The compiler generates efficient bit operations

where possible.

Masking and shifting

The classic method to extract a single bit in C is masking and shifting.

unsigned int bitword;

void foo( void )

TASKING VX-toolset for TriCore User Guide

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