Embedded c

Presented by
-Nandan Desai
Department of Electrical Engineering (FOE)
MEFGI
1


 To let the microcontroller do any task, we need to
program it.
 The 8051 microcontroller can be programmed in 2
ways:
1. Using Assembly Language
2. Using Embedded C language
 We, today, are going to concentrate on programming
of 8051 microcontroller using Embedded C.
 AN OBVIOUS QUESTION :
Programming the 8051 Microcontroller
2


 Advantages of C language:
1. Comparatively, modification is easy.
2. The code developing time is less.
 Disadvantages/Limitations:
1. Memory requirement is more.
2. More execution time is required.
So, the reason is…
3


 For programming the embedded hardware devices,
we need to use Embedded C language instead of our
conventional C language.
 The key differences between conventional C and
Embedded C are:
1. Embedded C has certain predefined variables for
registers, ports etc. which are in 8051 e.g. ACC, P1,
P2, TMOD etc.
2. We can run super loop (infinite loop) in embedded
C language.
Embedded C
4


 We know that the programming in C language is
solely done by dealing with different variables.
 In case of Embedded C, these variables are nothing
else but the memory locations of different memories
of the microcontroller like code memory(ROM), data
memory (RAM), external memory etc.
 To use these memory locations as variables, we need
to use data types.
 There are 7 different data types in embedded C for
8051… Lets go through them
Data types in Embedded C
5


 There are 7 data types in Embedded C for 8051:
1. unsigned char
This data type is used to define an unsigned 8-bit
variable. All 8-bits of this variable are used to specify data.
Hence the range of this data type is (0)10 𝑡𝑜 255 10.
e.g. unsigned char count;
2. signed char
This data type is used to define a signed 8-bit variable.
Here MSB of variable is used to show sign (+/-) while rest 7
bits are used to specify the magnitude of the variable. Hence
the range of this data type is (−128)10 𝑡𝑜 127 10.
e.g. signed char temp;
7 Data types
6


3. unsigned int
This data type is used to define a 16-bit variable.
Hence from this we can comment that this data types
combines any 2 memory locations of the data memory
as one variable. Here all 16 bits are used to specify data.
So the range of this data type is (0)10 𝑡𝑜 (65535)10.
4. signed int
This data type is used to define a signed variable
like signed char but of 16-bit size. Hence its range is
(−32768)10 𝑡𝑜 (32767)10.
continued...
7


5. sfr
This is an 8-bit data type used for defining names of
Special Function Registers (SFR’s) that are located in
RAM memory locations 80 H to FF H only.
e.g. sfr P0 = 0x80;
6. bit
This data type is used to access single bits from the
bit-addressable area of RAM.
e.g. bit MYBIT = 0x32;
continued...
8


7. sbit
The sbit data type is the one which is used to define
or rather access single bits of the bit addressable SFR’s
of 8051 microcontroller.
e.g. sbit En = P2^0;
continued...
9


 The decision control structures are used to decide
whether to execute a particular block of code
depending on the condition specified.
 Following are some decision control structures:
1. if statement
2. if…else statement
3. elseif ladder
Decision control structures
10


if and if...else statement
if statement
if(condition)
{
statement-1;
statement-2;
……..
}
 if...else statement
if(condition)
{
statement-1;
statement-2;
………
}
else
{
statement n;
} 11


 The loop statements are the one which are used
when we want to execute a certain block of code for
more than one times either depending on situation
or by a predefined number of times.
 Embedded C is basically having two loop
statements:
1. for loop
2. while loop
 Let us see on their formats:
Loop statements
12


for loops are used to repeat any particular
piece of code a predefined number of times.
for(initializations ; conditions ; updates)
{
statement-1;
statement-2;
………
}
for loop
13

 while loop also has the provision to repeat a certain
block of code but here the block is repeated
depending on the condition specified.
 The loop keeps on repeating until the condition
becomes false.
 Format of while loop is:
while(condition)
{
statement-1;
statement- 2;
………
}
while loop
14


 break
The break statement, whenever is encountered in the
loop, it forces the control to terminate the loop in which
it is written.
 continue
Whenever this statement is encountered in any loop,
the statements in the loop after it won’t be executed i.e.
will be skipped and again control will be transferred to
check the condition of the loop.
break & continue statements
15


#include <reg51.h> header file
sbit <name>=<bit address>; sfr bit definitions
sfr <name>=<sfr address>; sfr definition
Data-type udf1(data-type var_name); User defined
function
Data-type udf2(data-type var_name);
void main(void) main function
{
statement-1;
statement-2;
…….. ;
Format of any C Program
16

………;
udf1(value);
………; User defined function call
udf2(value);
}
Data-type udf1(data-type var_name)
{ statement-block;
return(ret_value);
}
Similarly 2nd function udf2 is defined…
continue…
17


 Sometimes, there comes a situation in which in a
program a group of statements is used frequently.
 Writing these statements again & again makes our
program clumsy to write as well as it consumes more
memory space.
 To overcome this problem there is a facility in C
language to define a function. In function we can
write the particular group of statements which is
getting repeated continuously.
 Now anytime when we want to use that code group,
we just have to call the function and its done.
Functions
18


1. No arguments, no return values
2. With no arguments and a return value
3. With arguments but no return value
4. With arguments and return value
Types of functions
19


 There are 3 ways to deal with a function:
1. Define first, then use
2. Do prototyping (i.e. Define first, use after main() )
3. Do prototyping in header file
 Let us see all the 3 in brief:
 Define first, then use
In this case, before writing the main function, we
define the user-defined function and then use it in
main() function whenever required.
Using a function
20


 Do prototyping and define after main function
In this case the function name, data type and
argument data type are specified before writing main
function to declare that we’ll later implement this
function.
 Do prototyping in header file
In this case, define the function in a (user defined)
header file and then just include that header file in your
program.
continued…
21

Embedded c

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