我们打开intrins.h文件
/*--------------------------------------------------------------------------
INTRINS.H
Intrinsic functions for C51.
Copyright (c) 1988-2010 Keil Elektronik GmbH and ARM Germany GmbH
All rights reserved.
--------------------------------------------------------------------------*/
#ifndef __INTRINS_H__
#define __INTRINS_H__
#pragma SAVE
#if defined (__CX2__)
#pragma FUNCTIONS(STATIC)
/* intrinsic functions are reentrant, but need static attribute */
#endif
extern void _nop_ (void);
extern bit _testbit_ (bit);
extern unsigned char _cror_ (unsigned char, unsigned char);
extern unsigned int _iror_ (unsigned int, unsigned char);
extern unsigned long _lror_ (unsigned long, unsigned char);
extern unsigned char _crol_ (unsigned char, unsigned char);
extern unsigned int _irol_ (unsigned int, unsigned char);
extern unsigned long _lrol_ (unsigned long, unsigned char);
extern unsigned char _chkfloat_(float);
#if defined (__CX2__)
extern int abs (int);
extern void _illop_ (void);
#endif
#if !defined (__CX2__)
extern void _push_ (unsigned char _sfr);
extern void _pop_ (unsigned char _sfr);
#endif
#pragma RESTORE
#endif
可以看到如上函数可以调用，我们具体对每个函数进行讲解一下。
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