Keil C51 Cross Compiler - gmitWEB

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Absolute Variable Location • The _at_ keyword is used to assign an absolute memory address to a variable – Useful for accessing memory mapped peripherals or specific memory locations – Syntax • type [memory_space] variable_name _at_ constant • unsigned char xdata lcd _at_ 0x8000 – Absolute variables may not be initialised Embedded Systems 2 2 - 34 C Programming
<strong>C51</strong> Pointers • Generic pointers – Same as ANSI C pointers – char *ptr; – Stored using 3 bytes – Can be used to access any memory space – Code generated executes more slowly than memory specific pointers • Memory Specific Pointers – Specify the memory area pointed to – char data *ptr1; //pointer to char in data memory – Stored as 1 (data, idata) or 2 bytes (code or xdata) – Can also specify where pointer is stored • char data * xdata ptr2; //pointer to data stored in xdata Embedded Systems 2 2 - 35 C Programming
Page 1 and 2: Keil C51 Cross Compiler • ANSI C
Page 3 and 4: C51 Keywords Embedded Systems 2 2 -
Page 5 and 6: C51 Memory Models • Small - All v
Page 7 and 8: C51 Memory Types • Memory type ex
Page 9 and 10: C51 Memory Types • bdata - Bit ad
Page 11 and 12: Example Code (1) sbit input = P1^0;
Page 13 and 14: Wait Loops • In some applications
Page 15 and 16: C Bitwise Operators • NOT ~ char
Page 17 and 18: C Logical Operators • Bitwise ope
Page 19 and 20: Accessing Port Pins • Writing to
Page 21 and 22: Example Code (3) //Program to read
Page 23 and 24: Example Code (4) //program to flash
Page 25 and 26: Software Delay • Use a for loop -
Page 27 and 28: Hardware Delay • Use timer 0 or t
Page 29 and 30: Re-entrant Functions • A re-entra
Page 31 and 32: Function Parameter Passing • Up t
Page 33: Interrupt Functions • Interrupt v

Keil C51 Cross Compiler - gmitWEB

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