78

Chapter 4. Creating Applications

SVCS Menu Item

Description

Undo Check Out

Undo the check out of a file.

Put Current Version

Save a local file in the SVCS database but still allow modifications to it.

Get Actual Version

Get a current read-only copy of a file from the SVCS.

Add file to Project

Add the file to the SVCS project.

Add file to Project

Add the file to the SVCS project.

Differences, History

Show SVCS information about the file.

Create Project

Create a SVCS project with the same name as the local µVision2 project.

4

MKS Source Integrity is pre-configured to create a project database on a server

and a local sandbox workspace on the workstation.

Intersolv PVCS is not pre-configured for creating and maintaining projects.

Writing Optimum Code

Many configuration parameters have influence on the code quality of your 8051

application. Although, for most applications the default tool setting generates

very good code, you should be aware of the parameters that improve code

density and execution speed. The code optimization techniques are described in

this section.

Memory Models and Memory Types

The most significant impact on code size and execution speed has the memory

model. The memory model influences variable accesses. Refer to “Memory

Models” on page 35 for detailed information. The memory model is selected in

the Options for Target – Target dialog page.

Getting Started and Creating Applications

79

With Global Register Optimization

Without Global Register Optimization

main () {

4

unsigned char i;

unsigned char a;

while (1) {

i = input ();

/* get number of values */

?C0001:

?C0001:

LCALL

input

LCALL

input

;- 'i' assigned to 'R6' -

MOV

DPTR,#i

MOV

R6,AR7

MOV

A,R7

MOV

@DPTR,A

do {

a = input ();

/* get input value */

?C0005:

?C0005:

LCALL

input

LCALL

input

;- 'a' assigned to 'R7' -

MOV

DPTR,#a

MOV

R5,AR7

MOV

A,R7

MOVX

@DPTR,A

output (a);

/* output value */

LCALL

_output

LCALL

_output

} while (--i);

/* decrement values */

DJNZ

R6,?C0005

MOV

DPTR,#i

MOVX

A,@DPTR

DEC

A

MOVX

@DPTR,A

JNZ

?C0005

}

SJMP

?C0001

SJMP

?C0001

}

RET

RET

Code Size: 18 Bytes

Code Size: 30 Bytes

80

Chapter 4. Creating Applications

Dialog Item

Description

Define

outputs the C51 DEFINE directive to enter preprocessor symbols.

Undefine

is only available in the Group and File Options dialog and allows you to

remove DEFINE symbols that are specified at the higher target or group

level.

Code Optimization

specifies C51 OPTIMIZE level. Typical you will not alter the default. With

Level

the highest level “9: Common block subroutine packing” the compiler

detects multiple instruction sequences and packs such code into

subroutines. While analyzing the code, the compiler also tries to replace

sequences with cheaper instructions. Since the compiler inserts sub-

routines and CALL instructions, the execution speed of the optimized code

might be slower. Typical this level is interesting to optimize the code

density.

Code Optimization

You can optimize for execution speed or code size. With “Favor Code

Emphasis

Size”, the C51 Compiler uses library calls instead of fast replacement code.

Global Register

enables the “Global Register Optimization”. Refer to page 79 for details.

Optimization

Getting Started and Creating Applications

81

Dialog Item

Description

Don't use absolute

disables absolute register addressing for registers R0 through R7.

The

register accesses

code will be slightly longer, since C51 cannot use ARx symbols, i.e. in

PUSH or POP instructions and needs to insert replace code. However the

code will be independent of the selected register bank.

Warnings

selects the C51 warninglevel. Warninglevel 0 disables all warnings.

Bits to round for float

determines the number of bits to rounded before a floating-point compare is

compare

executed.

Interrupt vectors at

instructs the C51 Compiler to generate interrupt vectors for interrupt

address

functions and specifies the base address for the interrupt vector table.

Keep Variables in

tells the C51 Compiler to order the variables in memory according their

Order

definition in the C source file. This option does not influence code quality.

Enable ANSI interger

expressions used in if statements are promoted from smaller types to

promotion rules

integer expressions before comparison. This gives typically longer code,

but is required to be ANSI compatible.

Misc Controls

allows you to enter special C51 directives. You may need such options

when you are using very new 8051 devices that require special directives.

Compiler Control

displays the C51 Compiler invocation string. Allows you can verify the

String

compiler options currently for your source files.