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Questions tagged [c51]

C51 is a C language compiler for the 8051 family of microcontrollers

33 questions
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Why does using data instead of xdata significantly reduce code space

I have tried searching for an answer to this but can not find a definitive reason. I am trying to optimise some 8051 C code to reduce code space. I made the following change.. xdata unsigned char a, b; to data unsigned char a, b; ... and saw my…
user968722
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How to reference a pointer to pdata or idata without using generic pointer?

Using Keil C51 on an 8051 target. I have a set of functions that take a pointer to a structure. The structure will only live in pdata or idata. Due to size constraints and memory mapping magic, I can't condense all structures into the same memory…
David Stover
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Keil uVision (C51 compiler), what is meaning of unary operator "!"?

I'm programming with Keil uVision 4. I have some code like this: sbit X = P3 ^ 3; // X is third bit of P3 register ... while (1) { X = !X; // X equals not X ?! if (X == 0) printf("0"); else printf("1"); …
Filippo Lauria
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Keil C51 doesn't allocate memory for struct pointers at compile time

I'm trying to created a linked list of structs for an EFM8 microcontroller project. I want to have the compiler allocate memory for all of the nodes at compile time. The issue I'm having is that no memory is being allocated for struct…
Mike Szczys
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Wrong output sprintf C51 8051 MCU embedded system

I have the following fragment of C code for an AT89S52 microcontroller: unsigned char x = 0x10; unsigned char str[21]; sprintf(str, "%u", (x >> 4) ); sprintf function prototype in stdio.h: extern int sprintf (char *, const char *, ...); Can…
MLuna
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array [] vs pointer * - why will the first code fail in C?

I'm using a Keil C51 compiler to program a 8051 microcontroller. For some reason my code didn't run - I managed to track down the bug, but I still have difficulties understanding it. Why is the first code wrong, comparing to the other one? It's…
Suryu
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Arithmetic operation in Assembler

I'm in the beginning of studying assembler, and I need to calculate (x1+x2)/(x1*x2), and I'm totally don't understand how to do it. Here's my variation of solving, but my teacher says there's a better way to do it. org 0000h x1: equ 30h x2: equ…
Alexander Gess
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Invalid use of macro pasting in macro in Eclipse

Hello I have the following problem: IDE: Eclipse Version: 2018-12 (4.10.0) with the Keil C51 plugin (for Language Mapping) Compiler (external): Wickenhäuser uc51 Problem here: Eclipse Bad Character Sequence Keil Language mapping is using this…
Tick Tac Joe
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KEIL for C51 and have some problems with error like syntax error near unsigned

I am working with Keil for 80C51 and I use C51 for coding. However, I have some problem in my compiling. My code is like following: #include #define uchar unsigned char #define LED P2 sbit SH=P0^0; sbit DATA=P3^0; sbit CLK=P3^1; void…
Sheng Nee
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How to use buffer to read and write using serial port in 8051 MCU

I am using keil c51 compiler. I transmit data from my pc to MCU using serial port it works best. When I transmit data from my MCU to PC then also it works best. But when I transmit data to MCU and then store it to buffer character pointer and again…
Balvant Jat
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Adapting sbit for GCC

I'm writing a test harness for some C modules, one of which contains the "sbit" keyword. The code was initially written for the Keil C51 compiler, where sbit is used to define a bit within an sfr, more information here. However, I'm writing the test…
Andy
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I want to print a multidimensional char array on an lcd in c51 (Keil)

(The array is intialised with a bunch of characters) I'm also getting an error saying "Data segment too large" when I make the array bigger. How do I copy the array from "CODE" to "XDATA"? or is this not the problem? EDIT: Also when I call the…
user3277087
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printf() results in gibberish

I have this code: unsigned char *command = "0000"; unsigned char foo = (hex_char_to_int(command[0]) << 4) | hex_char_to_int(command[1]); unsigned char bar = (hex_char_to_int(command[2]) << 4) | hex_char_to_int(command[3]); printf("foo: %02x, bar:…
Drew
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Emulated eeprom in C8051F380 Silabs controllef

In my project on the C8051F380 controller, it is necessary to save parameters after shutdown, I am, as in the usual case, decided to use emulated EEPROM But unfortunately, I couldn't find a detailed explanation on this topic, Yes, there are some…
B Z
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clock program (6 seven-segment digital tubes) in c51

/*Use C51 to write the program for STC89C52 single-chip microcomputer, the clock frequency is 11.0592MHZ*/ #include #define unchar unsigned char #define unint unsigned int #define unlint unsigned long int #define fosc 11059200ul #define N…
マイドアリ
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