Giáo trình Kỹ thuật vi xử lý - Chương 4: Viết chương trình cho MCU 8051
Häc tr×nh IV. ViÕt ch-¬ng tr×nh cho MCU 8051
IV-1. Giíi thiÖu chung vÒ viÕt ch-¬ng tr×nh cho MCU 8051.
1/ CPU vµ ng«n ng÷ m¸y.
- Qua c¸c phÇn ®· nghiªn cøu ë trªn ta thÊy mét Kit VSL hay mét PC bao giê
còng bao gåm hai phÇn ®ã lµ:
- PhÇn cøng (HARD WARE).
- PhÇn mÒm (SOFT WARE).
- Ta l¹i biÕt phÇn cøng (hard ware) lµ mét tËp hîp c¸c m¹ch ®iÖn sè, tËp hîp c¸c
m¹ch ®iÖn nµy sÏ kh«ng thÓ ho¹t ®éng ®-îc nÕu kh«ng cã c¸c phÇn mÒm ®iÒu
khiÓn nã. Ta cã thÓ gäi phÇn mÒm cña mét hÖ thèng VSL lµ linh hån cña nã bëi vú
nÕu kh«ng cã nã th× m¸y tÝnh kh«ng thÓ ho¹t ®éng ®-îc.
- PhÇn mÒm cña mét hÖ thèng VSL l¹i bao gåm 2 phÇn ®ã lµ phÇn mÒm hÖ thèng vµ
phÇn mÒm øng dông.
- PhÇn mÒm hÖ thèng dïng ®Ó ®iÒu khiÓn ch-¬ng tr×nh nh- lµ phÇn mÒm
WINDOW,
MSDOS..
- PhÇn mÒm øng dông lµ c¸c phÇn mÒm dïng ®Ó ch¹y ch-¬ng tr×nh nh- lµ phÇn
mÒm BASCOM, $S51, C, C++......
- Nh-ng mét ®iÒu ®¸ng chó ý lµ mét hÖ thèng VSL chØ cã kh¶ n¨ng hiÓu ®-îc c¸c
ký tù lµ “0” vµ “1” bëi v× mét hÖ thèng VSL chÝnh lµ mét tæ hîp tËp hîp c¸c m¹ch
®iÖn nªn nã chØ cã kh¶ n¨ng hiÓu ®-îc mét tËp lÖnh bao gåm c¸c ký tù “0” vµ
“1”®-îc viÕt d-íi d¹ng nh÷ng tõ m· hay cßn gäi lµ nh÷ng chØ lÖnh.
- Nh-ng ta l¹i biÕt mét ch-¬ng tr×nh øng dông bao giê còng rÊt dµi cã khi tíi hµng
ngh×n trang bëi vËy viÖc viÕt mét ch-¬ng tr×nh b»ng ng«n ng÷ m¸y sÏ rÊt phøc t¹p
cho ng-êi viÕt v× nã khã nhí vµ dÔ g©y nhÇm lÉn bëi mét chuçi nh÷ng ký tù chØ lµ
nh÷ng sè “0” vµ “1”, bëi vËy viÖc cho ra ®êi nh÷ng phÇn mÒm võa gÇn gòi víi con
ng-êi, võa lµm cho m¸y tÝnh hiÓu ®-îc lµ ®iÒu cÇn thiÕt.
- XuÊt ph¸t tõ c¸ch ®Æt vÊn ®Ò trªn cho nªn song song víi viÖc cho ra ®êi c¸c phÇn
cøng c¸c h·ng lín trªn thÕ giíi ®· cho ra ®êi rÊt nhiÒu phÇn mÒm kh¸c nhau cßn gäi
lµ ng«n ng÷ . Nh×n chung chóng thuéc 3 ng«n ng÷ lo¹i c¬ b¶n sau:
- Ng«n ng÷ m¸y (MACHINE LANGUAGE)
- Ng«n ng÷ bËc thÊp (LOW DEGREE). Nh- lµ ASSEMBLY.
- Ng«n ng÷ bËc cao (HIGH DEGREE), nh- lµ PASCAL, C, C++, BASIC.....
* Vµ ngµy nay ng-êi ta chØ viÕt ch-¬ng tr×nh b»ng ng«n ng÷ bËc cao (rÊt Ýt khi viÕt
b»ng ng«n ng÷ bËc thÊp), vµ ng-êi ta sö dông mét tr×nh liªn kÕt (COMPILE) ®Ó
chuyÓn ®æi tõ ng«n ng÷ bËc cao hay ng«n ng÷ bËc thÊp ra ng«n ng÷ m¸y
- ViÖc viÕt ch-¬ng tr×nh b»ng ng«n ng÷ bËc thÊp tuy dÔ hiÓu vµ ®é chÝnh x¸c cao
nh-ng c©u lÖnh rÊt dµi v× vËy viÖc viÕt ch-¬ng tr×nh rÊt mÊt thêi gian vµ hÇu hÕt c¸c
nhµ s¶n xuÊt phÇn mÒm kh«ng sö dông lo¹i ng«n ng÷ nµy.
- Ng«n ng÷ bËc cao rÊt ®a d¹ng nªn tuú theo tõng lÜnh vùc mµ ng-êi ta lùa chän
phÇn mÒm cho phï hîp.
- §èi víi c¸c chuyªn ngµnh §iÖn, §iÖn tö ng-êi ta hay dïng c¸c phÇn mÒm C,
C++, BASIC vµ ®«i khi ng-êi ta dïng ASSEMBLY.
2/ Ng«n ng÷ ASSEMBLY.
- ASSEMBLY lµ ng«n ng÷ gÇn gòi nhÊt víi ng«n ng÷ m¸y vµ nã t¹o ra nh÷ng gîi
nhí trong c©u lÖnh lµm cho ng-êi lËp tr×nh dÔ hiÓu ®Ó viÕt ch-¬ng tr×nh.
- Do dÔ hiÓu nªn dÔ söa lçi ch-¬ng tr×nh.
- Do nã gÇn víi ng«n ng÷ m¸y nªn ®é chÝnh s¸c cña ch-¬ng tr×nh cao.
- Nã cã nh-îc ®iÓm lµ c©u lÖnh rÊt dµi nªn viÕt l©u vµ ch-¬ng tr×nh ch¹y chËm.
EG.
- Mét c©u lÖnh cña ASSEMBLYnh- sau:
- N¹p néi dung chøa trong thanh ghi B
LD A,B
vµo thanh ghi A (FOR Z80)
- LÖnh nµy ®-îc ph©n tÝch nh- sau:
LD = OPCODE - gäi lµ m· lÖnh
A,B gäi lµ c¸c to¸n h¹ng (OPERAND)
A lµ to¸n h¹ng ®Ých
B lµ to¸n h¹ng nguån.
- LÖnh nµy ®-îc m· ho¸ nh- sau:
0111.100(B) = 78(H).
EG.
LD A,C. N¹p néi dung chøa trong thanh ghi C vµo thanh ghi A (cho Z80).
- LÖnh nµy ®-îc m· ho¸ nh- sau:
0111.1001(B) = 79(H).
EG.
LÖnh ADD. Hai sè nhÞ ph©n cña 8051 ®-îc m· ho¸ nh- sau:
1011.0011(B) = B3(H).
IV- 2. CÊu tróc cña ch-¬ng tr×nh. (STRUCTURED PPROGRAMMING)
- CÊu tróc cña ch-¬ng tr×nh hay lËp tr×nh cã cÊu tróc lµ mét kü thuËt dïng ®Ó tæ
chøc vµ viÕt ch-¬ng tr×nh sao cho gi¶m ®-îc ®é phøc t¹p, dÔ hiÓu, dÔ gì rèi , dÔ
thay ®æi. ý t-ëng cña ch-¬ng tr×nh ®-îc cÊu tróc mét c¸ch râ rµng m¹ch l¹c. §Ó
ph¶n ¸nh ý t-ëng ®ã mét ch-¬ng tr×nh hay mét ng-êi viÕt ch-¬ng tr×nh ®Òu cã thÓ
sö dông ba lo¹i cÊu tróc c¬ b¶n sau ®©y:
- CÊu tróc d¹ng ph¸t biÓu (STATMEN).
- CÊu tróc d¹ng vßng lÆp (LOOP).
- CÊu tróc d¹ng lùa chän (CHOICE)
1/ C¸c ph¸t biÓu
- §ã lÇ viÖc g¸n mét gi¸ trÞ cho mét biÕn nµo ®ã nh-:
- [ COUNT = 0].
- HoÆc gäi mét ch-¬ng tr×nh con nh-:
- PRINT-STRING.
2/ CÊu tróc vßng lÆp.
- §©y lµ mét cÊu tróc c¬ b¶n ®-îc øng dông rÊt nhiÒu, cã 2 d¹ng vßng lÆp nh- sau:
* Ph¸t biÓu WHILE- DO.
EG. Trong khi cê nhí cña 8051 cßn b»ng 1, mét ph¸t biÓu ®-îc thùc thi nh- sau:
- Gi¶i m· (PSEUDO):
WHILE [C = = 1] DO.
ENTER
C = 1
?
EXIT
STATMENT
- Ch-¬ng tr×nh ®-îc viÕt cho 8051 nh- sau:
ENTER
STTATEMENT........
JMP ENTER.
EXIT ...... (CONTINUE).
* Ph¸t biÓu REPEAT- UNTIL.
JNC EXIT
- CÊu tróc d¹ng nµy ®-îc dïng cho c¸c bµi to¸n mµ c«ng viÖc ®-îc lÆp l¹i Ýt nhÊt 1
lÇn.
- Gi¶ m·:
REPEAT
[ACC = @POINTER].
[INCREAMENT POINTER].
UNTIL
[ACC = = “Z” OR ACC = = 0].
- L-u ®å:
ENTER
GET A CHRACTER
INCREAMENT
POINT
NO
NO
CHARACTER = Z ?
CHARACTER = 0 ?
YES
YES
EXIT
- Ch-¬ng tr×nh cho 8051 ®-îc viÕt nh- sau:
STATEMENT:
MOV A,@R0.
INC R0.
JZ EXIT
CJNE A,#”Z”,STATEMENT
RET
EXIT:
3/ CÊu tróc lùa chän.
- Lµ cÊu tróc t¹o nªn sù rÏ nh¸nh trªn ®-êng.
* Ph¸t biÓu IF- THEN- ELSE.
EG.
- H·y viÕt mét chuçi lÖnh ®Ó nhËp vµ kiÓm tra mét ký tù cña PORT nèi tiÕp. NÕu ký
tù lµ m· ASCII hiÓn thÞ ®-îc cho hiÓn thÞ ký tù., ng-îc l¹i cho hiÓn thÞ ký tù (. ).
- Gi¶ m·:
[INPUT CHARACTER]
IF [CHARACTER = = GRAPHIC]
THEN [ECHO CHARACTER]
ELSE [ECHO “.” ].
- L-u ®å:
ENTER
INPUT CHRACTER
GRAPHIC
CHARACTER
NO
YES
ECHO
“.”
ECHO
CHARD
ACTER
EXIT
- Ch-¬ng tr×nh ®-îc viÕt cho 8051.
ENTER:
ACALL INCH
ACALL ISGPH
JNC STMENT2
STMENT1:
STMENT2:
ACALL OUTCHR
JMP EXIT
MOV A,#’.’
ACALL OUTCHR
EXIT: (CONTINUE)
ACALL INCH
ACALL ISGRPH
JC SKIP
MOV A,#’.’
ACALL OUTCHR
SKIP
(CONTINUE)
DO BEGIN
WHILE[1]
[INPUT CHARACTER]
IF [CHARACTER = = GRAPHIC]
THEN [ECHO CHARACTER]
ELSE [ECHO’.’ ]
END
* Ph¸t biÓu CASE:
- Ph¸t biÓu CASE lµ biÕn thÓ cña ph¸t biÓu IF THEN, ®-îc øng dông khi cã mét
trong nhiÒu ph¸t biÓu ®-îc lùa chän.
- Gi¶ m·:
CASE [EXPRESSION] OF
0: [STATEMENT 0]
1: [ STATEMENT1]
2: [STATEMENT 2]
N: [STATEMENT N]
[DEFAULT STATEMENT]
END - CASE
- L-u ®å.
ENTER
EXPRES.N
EXPRESS.3
EXPRESS.2
EXPRESS.1
FALSE
FALSE
FALSE
FALSE
TRUE
TRUE
TRUE
TRUE
STMEN. N
STMENT 3
DEFALT
ST.MEN
STMEN. 1
STMENT.2
EXIT
IV-3. C¸c vÝ dô vÒ lËp ch-¬ng tr×nh cho 8051.
§Ó viÕt ch-¬ng tr×nh cho 8051 ta cã thÓ thùc hiÖn b»ng c¸ch viÕt ch-¬ng tr×nh
b»ng ng«n ng«n ng÷ ASSEBLY hoÆc b»ng bÊt kú mét lo¹i ng«n ng÷ kh¸c. §Ó vÊn
®Ò tr×nh bÇy ®-îc ®¬n gi¶n vµ ng-êi häc dÔ thùc hiÖn, trong tµi liÖu nµy xin tr×nh
bÇy hai c¸ch viÕt b»ng ng«n ng÷ ASSEMBLY vµ b»ng ng«n ng÷ BASCOM, chñ
yÕu lµ b»ng ng«n ng÷ BASCOM, chØ cã nh÷ng vÝ dô ®¬n gi¶n míi tr×nh bµy b»ng
ng«n ng÷ ASSEMBLY.
1/ ViÕt ch-¬ng tr×nh b»ng ng«n ng÷ sEMBLY.
§Ó viÕt ch-¬ng trinh b»ng ng«n ng÷ ASSEMBLY ta cÇn n¾m v÷ng tËp lÖnh cña
8051 ®· ®-îc tr×nh bÇy á môc III-5.
VÝ dô 1:
H·y viÕt ch-¬ng tr×nh ®Ó t¹o xung vu«ng t¹i ch©n P1.1, víi F= 10HZ.
$MOD51
ORG 0000H
LOOP:
SETB P1.1
LCALL DELAY
CLR P1.1
;P1.1=1
;P1.1= 0
LCALL DELAY
LJMP LOOP
DELAY:
MOV R2,#200
X: DJNZ R1,X
MOV r1,#250
MOV R1,#250
DJNZ R2,X
RET
END.
VÝ dô 2:
H·y viÕt ch-¬ng tr×nh ®Ó ®iÒu khiÓn 3 LED g¾n vµo PORT1 sao cho c¸c LED s¸ng
dÇn tõng c¸i mét.
( Anode cña c¸c LED nèi lªn d-¬ng nguån, kh«ng dïng vßng lÆp).
; B¾t ®Çu ch-¬ng tr×nh
$MOD51 ORG 0000H
LOOP
MOV A,#1111.1110B.
MOV P1,A
; P1.0 = 0.
LCALL
RL
MOV P1,A
LCALL
RL
DELAY
A
; A = 1111.1101B
; P1.1 = 0
DELAY
A
P1,A
; A = 1111.1011B
; P1.2 =0
MOV
LCALL
RL
LCALL
SJMP
DELAY
A
DELAY
LOOP
R1,#250
R2,#200
R1,X
; A = 1111.0111B
DELAY:MOV
MOV
X: DJNZ
MOV
R1,#250
R2,X
DJNZ
RET
END
VÝ dô 3:
; ViÕt ch-¬ng tr×nh ®Ó ®iÒu khiÓn 8 LED g¾n vµo PORT1, sao cho c¸c lED s¸ng dÇn
lªn.
; Ch-¬ng tr×nh b¾t ®Çu.
$MOD51ORG 0000H
LOOP: MOV A,#1111.1110B ; A = 01H
NEXT: MOV P1,A
; P1.0 = 1.
LCALL
CLR
RLC
DELAY
C
A
; C =0
; A = 1111.1100B
JC
SJMP
DELAY: MOV
MOV
NEXT
LOOP
R1,#250
R2,#200
R1,X
R1,#250
R2,X
; C = 1 th× tiÕp tôc.
X:
DJNZ
MOV
DJNZ
RET
END.
2/ ViÕt ch-¬ng tr×nh b»ng ng«n ng÷ BASCOM
A/ Gi¬Ý thiÖu tËp lÖnh cña BASCOM.
(BASCOM Language Fundamenttals).
Language Fundamentals
(Ng«n ng÷ c¬ b¶n cña BASCOM)
Characters from the BASCOM character set are put together to form labels,
keywords, variables and operators.
These in turn combine to form statements that make up a program.
This chapter describes the character set and the format of BASCOM program lines.
In particular, it discusses:
* The specific characters in the character set and the special meanings of some
characters.
* The format of a line in a BASCOM program.
*Line labels.
* Program line length.
Character Set
(Bé ký tù cña BASCOM)
The BASCOM BASIC character set consist of alphabetic characters,
numeric characters, and special characters.
The alphabetic characters in BASCOM are the uppercase letters (A-Z) and
lowercase letters (az) of the alphabet.
The BASCOM numeric characters are the digits 0-9.
The letters can be used as parts of hexadecimal numbers.
The following characters have special meanings in BASCOM statements and
expressions:
Character
name
ENTER
Terminates input of a line (KÕt thóc viÖc nhËp d÷ liÖu cho 1 dßng)
Blank ( or space) (Kho¶ng trèng)
'
Single quotation mark (apostrophe)
(DÊu ngoÆc ®¬n)
*
Asterisks (multiplication symbol)
(Dêu sao, biÓu t-îng cña phÐp nh©n)
Plus sign
(DÊu céng)
Comma
+
,
(Dêu phÈy)
Minus sign
-
(DÊu trõ)
.
Period (decimal point)
(DÊu chÊm thËp ph©n)
Slash (division symbol) will be handled as \
(DÊu g¹ch chÐo- biÓu t-îng cña phÐp chia)
Colon
/
:
(DÊu hai chÊm)
Double quotation mark
(DÊu ngoÆc kÐp)
"
;
Semicolon
(DÊu chÊm phÈy)
Less than
(DÊu nhá h¬n)
Equal sign (assignment symbol or relational operator)
(DÊu b»ng)
Greater than
(DÊu lín h¬n)
Backslash (integer/word division symbol)
(DÊu g¹ch chÐo ng-îc)
<
=
>
\
The BASCOM program line
(Dßng lÖnh cña BASCOM)
BASCOM program lines have the following syntax:
(Dßng lÖnh cã d¹ng nh- sau)
[[line-identifier]] [[statement]] [[:statement]] ... [[comment]]
Using Line Identifiers
(NhËn d¹ng c¸c dßng lÖnh)
BASCOM support one type of line-identifier; alphanumeric line labels:
An alphabetic line label may be any combination of from 1 to 32 letters and digits,
starting with a letter and ending with a colon.
BASCOM keywords are not permitted. The following are valid alphanumeric line
labels:
Alpha:
ScreenSUB:
Test3A:
Case is not significant. The following line labels are equivalent:
alpha:
Alpha:
ALPHA:
Line labels may begin in any column, as long as they are the first characters other
than blanks on the line.
Blanks are not allowed between an alphabetic label and the colon following it.
A line can have only one label.
BASCOM Statements
(Ph¸t biÓu cña BASCOM)
A BASCOM statement is either " executable" or " nonexecutable" .
An executable statement advances the flow of a programs logic by telling the
program what tot do next.
Non executable statement perform tasks such as allocating storage for variables,
declaring and defining variable types.
The following BASCOM statements are examples of nonexecutable statements:
*
*
REM or (starts a comment)
DIM
A " comment" is a nonexecutable statement used to clarify a programs operation
and purpose.
A comment is introduced by the REM statement or a single quote character(').
The following lines are equivalent:
PRINT " Quantity remaining" : REM Print report label.
PRINT " Quantity remaining" ' Print report label.
More than one BASCOM statement can be placed on a line, but colons(:) must
separate statements, as illustrated below.
FOR I = 1 TO 5 : PRINT " Gday, mate." : NEXT I
BASCOM LineLength
If you enter your programs using the built-in editor, you are not limited to any line
length, although it is advised to shorten your lines to 80 characters for clarity.
Data Types
(KiÓu d÷ liÖu)
Every variable in BASCOM has a data type that determines what can be stored in
the variable. The next section summarizes the elementary data types.
Elementary Data Types
(C¸c kiÓu d÷ liÖu c¬ b¶n)
*
*
Bit (1/8 byte)
Byte (1 byte).
Bytes are stores as unsigned 8-bit binary numbers ranging in value from 0 to 255.
Integer (two bytes).
*
Integers are stored as signed sixteen-bit binary numbers ranging in value from -
32,768 to +32,767.
*
Word (two bytes).
Words are stored as unsigned sixteen-bit binary numbers ranging in value from 0
to 65535.
*
Long (four bytes).
Longs are stored as signed 32-bit binary numbers ranging in value from -
2147483648 to 2147483647.
*
Single
Singles are stored as signed 32 bit binary numbers.
String (up to 254 bytes).
*
Strings are stored as bytes and are terminated with a 0-byte.
A string dimensioned with a length of 10 bytes will occupy 11 bytes.
Variables can be stored internal (default) or external.
(C¸c biÕn sè cã thÓ ®· ®-îc l-u tr÷ trong bé nhí hoÆc l;-u tr÷ ë bªn ngoµi )
Variables
(C¸c biÕn sè)
A variable is a name that refers to an object--a particular number.
(Tªn cña biÕn sè ®-îc tham kh¶o chi tiÕt ë môc nãi vÒ sè)
A numeric variable, can be assigned only a numeric value (either integer,byte long,
single or bit).
The following list shows some examples of variable assignments:
(B¶ng d-íi ®©y chØ ra c¸c vÝ dô vÒ viÖc g¸n biÕn sè nh- thÕ nµo)
*
*
*
A constant value:
A = 5
C = 1.1
The value of another numeric variable:
abc = def
k = g
The value obtained by combining other variables, constants, and
operators:
(C¸c to¸n tö):
Temp = a + 5
Temp = C + 5
Variable Names
(C¸c tªn cña biÕn sè)
A BASCOM variable name may contain up to 32 characters.
The characters allowed in a variable name are letters and numbers.
The first character in a variable name must be a letter.
A variable name cannot be a reserved word, but embedded reserved words are
allowed.
For example, the following statement is illegal because AND is a reserved word.
AND = 8
However, the following statement is legal:
ToAND = 8
Reserved words include all BASCOM commands, statements, function names,
internal registers and operator names.
(see BASCOM Reserved Words , for a complete list of reserved words).
You can specify a hexadecimal or binary number with the prefix &H or &B.
a = &HA , a = &B1010 and a = 10 are all the same.
Before assigning a variable you must tell the compiler about it with the DIM
statement.
Dim b1 As Bit, I as Integer, k as Byte , s As String * 10
You can also use DEFINT, DEFBIT, DEFBYTE and/or DEFWORD.
For example DEFINT c tells the compiler that all variables that are not dimensioned
and that are beginning with the character c are of the Integer type.
Expressions and Operators
(C¸c to¸n tö vµ c¸c c¸ch tr×nh bÇy)
This chapter discusses how to combine, modify, compare, or get information about
expressions by using the operators available in BASCOM.
Anytime you do a calculation you are using expressions and operators.
This chapter describes how expressions are formed and concludes by describing the
following kind of operators:
*
*
*
Arithmetic operators, used to perform calculations.
Relational operators, used to compare numeric values.
Logical operators, used to test conditions or manipulate individual
bits.
*
Functional operators, used to supplement simple operators.
Expressions and Operators
An expression can be a numeric constant, a variable, or a single value
obtained by combining constants, variables, and other expressions with operators.
Operators perform mathematical or logical operations on values.
The operators provides by BASCOM can be divided into four categories, as follows:
1.
2.
3.
4.
Arithmetic (Sè häc)
Relational (Quan hÖ)
Logical (Logic)
Functional (Hµm sè)
Arithmetic (Sè häc)
Arithmetic operators are +, - , * and \.
*
Integer
Integer division is denoted by the backslash (\).
Example:
Z = X \ Y
*
Modulo Arithmetic
Modulo arithmetic is denoted by the modulus operator MOD.
Modulo arithmetic provides the remainder, rather than the quotient,
of an
integer division.
Example: X = 10 \ 4 : remainder = 10 MOD 4
*
Overflow and division by zero
Division by zero, produces an error.
At this moment there is no message, so you have to insure yourself that such wont
happen.
Relational Operators
(C¸c to¸n tö quan hÖ)
Relational operators are used to compare two values as shown in the table below.
The result can be used to make a decision regarding program flow.
Operator
=
<>
<
Relation Tested Expression
Equality X = Y (B»ng)
Inequality X <> Y (Kh«ng b»ng)
Less than X < Y (Nhá h¬n)
>
<=
>=
Greater than X > Y (Lín h¬n)
Less than or equal toX <= Y (Nhá h¬n hoÆc b»ng)
Greater than or equal to X >= Y (Lín h¬n hoÆc b»ng)
Logical Operators
(C¸c to¸n tö Logic)
Logical operators perform tests on relations, bit manipulations, or Boolean
operators.
There are four operators in BASCOM, they are :
(Cã 4 to¸n tö Logic lµ):
Operator
NOT
Meaning
Logical complement
(Bï logic)
AND
OR
Conjunction
(KÕt hîp)
Disjunction
(Ph©n t¸ch)
XOR
Exclusive or
(HoÆc lo¹i trõ)
It is possible to use logical operators to test bytes for a particular bit pattern.
For example the AND operator can be used to mask all but one of the bits
of a status byte, while OR can be used to merge two bytes to create a particular
binary value.
Example
A = 63 And 19
PRINT A
A = 10 Or 9
PRINT A
Output
16
11
Floating point
(DÊu chÊm ®éng)
A new datatype is added to BASCOM : the single.
(Mét kiÓu d÷ liÖu míi ®-îc thªm vµo BASCOM ®ols lµ: SING (DUY NHAT)
Single numbers conform to the IEEE binary floating point standard.
An eight-bit exponent and 24 bit mantissa are supported.
Using four bytes, the format is shown below:
31 30________23 22______________________________0
S exponent mantiss
(sè mò)
(phÇn ®Þnh trÞ)
The exponent is biased by 128. Above 128 are positive exponents and
below are negative. The sign bit is 0 for positive numbers and 1 for
negative. The mantissa is stored in hidden bit normalized format so
that 24 bits of precision can be obtained.
All mathematical operations are supported by the single.
(TÊt c¶ c¸c to¸n tö to¸n cña phÐp to¸n th× ®-îc cung cÊp t¹i pphÇn d÷ liÖu SINH)
You can also convert a single to an integer or word or vise versa:
Dim I as Integer, S as Single
S = 100.1
I = S
'assign the single
'will convert the single to an integer
Take a look at the single.bas example for more information.
Arrays
(M¶ng)
Arrays are also a new extension to BASCOM.
An array is a set of sequentially indexed elements having the same type. Each
element of an array has a unique index number that identifies it. Changes made to
an element of an array do not affect the other elements.
The index must be a numeric constant, a byte, an integer or a word. This means that
an array can hold 65535 elements as a maximum. The minimum value is 1 and not
zero as in QB.
Arrays can be used on each place where a 'normal' variable is expected but there are
a few exceptions.
These exceptions are shown in the help topics.
Note that there are no BIT arrays in BASCOM-8051.
Example:
Dim a(10) as byte 'make an array named a,with 10 elements (1 to 10)
Dim c as Integer
For C = 1 To 10
a(c) = c
Print a(c)
'assign array element
'print it
Next
Strings
(Chuçi)
Strings can be up to 254 characters long in BASCOM.
To save memory you must sepcify how long each string must be with the DIM
statement.
Dim S As String * 10
This will reserve space for the string S with a length of 10 bytes. The actually length
is 11 bytes because a nul(0) is used to terminate the string.
You can concatenate string with the + sign.
Dim S As String * 10 , Z As String * 10
S = "test"
Z = S + "abc"
In QB you can assign a string with a value and add the original string (or a part of
it) too :.
S = "test"
S = "a" + s
This will result in the string "atest"
In BASCOM this is NOT possible because this would requiere a copy of the string.
In BASCOM the string S is assigned with "a" and on that moment the original
string S is destroyed. So you must make a copy of the string yourself in the event
you need this functionality.
B.BASCOM STATEMENTS
-1-
1WRESET, 1WREAD, 1WWRITE
-COMPILER DIRECTIVES-
#IF
#ELSE
#ENDIF
$ASM - $END ASM
$INCLUDE
$BAUD
$BGF
$CRYSTAL
$DEFAULT XRAM
$IRAMSTART
$LARGE
$LCD
$MAP
$NOBREAK
$NOINIT
$NONAN
$NONULL
$NOSP
$OBJ
$RAMSIZE
$RAMSTART
$REGFILE
$ROMSTART
$SERIALINPUT
$SERIALINPUT2LCD
$SERIALOUTPUT
$SIM
-A-
ABS
ALIAS
ASC
AVG
-B-
BITWAIT
BCD
BREAK
-C-
CALL
CLOSE
CLS
CHR
CONFIG
CONST
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