Download A1. AVR Assembler and Studio

IKI10230
Pengantar Organisasi Komputer
Kuliah no. A1: AVR Assembler & Studio
Sumber:
1. AVR Assembler.
2. AVR Studio
28 Februari 2003
Bobby Nazief ([email protected])
Qonita Shahab ([email protected])
bahan kuliah: http://www.cs.ui.ac.id/kuliah/iki10230/
1
Why RISC?
° Reduced Instruction Set Computing (RISC)
° Hanya terbatas jenis/jumlah instruksi untuk operasi
dasar
• Arithmetic, load/store, branches and jumps
• Instruksi umum dan sering digunakan: sederhana dan cepat
Top 10 80x86 Instructions
Rank
Instruction
Integer Average Percent total executed
1
load
22%
2
conditional branch
20%
3
compare
16%
4
store
12%
5
add
8%
6
and
6%
7
sub
5%
8
move register-register
4%
9
call
1%
10
return
1%
Total
96%
Simple instructions dominate instruction frequency
make common case: simple and fast
17
2
Why AVR 8-bit RISC ?
° RISC: kinerja (performance) komputer meningkat
• Pilihan teknologi rancangan prosesor modern (PowerPC, Sun
Sparc, MIPS dll)
• Fast with reduced complexity!
° Atmel AVR 8-bit RISC
• Sederhana (bentuk minimalis dari RISC): mudah dipelajari !
• Target operasi: microcontroller (embedded systems)
- Berbagai aplikasi dan peralatan elektronis (ponsel, home
appliances, mobil, dll)
- Controller untuk pabrik, proses kimia, mesin dll.
- “Vast opportunity”: karir, wira-usaha dll. (more embedded
computers than PCs!!!)
° Why not X86 (Intel, mikroprosesor paling populer)
• Terlalu rumit (complex): operasi beragam dan sangat banyak
variasinya
• Akses langsung ke register di PC kita? 
3
AVR Assembler
4
Bahasa Rakitan AVR
° Komputer (rangkaian dijital) hanya mengerti instruksi
mesin
° Assembly code: representasi tekstual (mudah dibaca
oleh manusia) dari instruksi mesin
• Setiap instruksi mesin (instruction sets) terdapat korespondensi
assembly code
• Kode tersebut: simbol dari operasi instruksi mesin
• Bahasa rakitan (assembly language): cara pemrograman
menggunakan assembly code (terdapat banyak bantuan untuk
memudahkan penulisan program).
° Assembler: sebuah program yang menerjemahkan
assembly code ke instruksi mesin.
5
Contoh Program
ldi
r16,0x8
ldi
r17,0x9
add
r16,r17
ldi
r18,0xff
sub
r18,r16
com r16
; r16 = 0x8 + 0x9 = 0x11
; r18 = 0xff - 0x11 = 0xee
; r16 = 0xee
nop
6
AVR Assembler: Kompilasi Program
7
Contoh Program.LST
000000 e008
ldi
r16,0x8
000001 e019
ldi
r17,0x9
000002 0f01
add
r16,r17
000003 ef2f
ldi
r18,0xff
000004 1b20
sub
r18,r16
000005 9500
com r16
000006 0000
nop
8
Pemrograman
Bahasa Rakitan AVR
9
Instruksi
° Bahasa Rakitan: setiap “statement” disebut
instruksi, merupakan eksekusi/operasi perintah
instruksi mesin
• Jadi setiap baris pada bahasa rakitan: berisi 1 (satu) perintah
saja (bandingkan dengan HLL!)
10
Syntax
° 1 instruksi per baris
° Format setiap baris instruksi:
1. [label:] directive
2. [label:] instruction
3. komentar
[operands]
[operands]
[komentar]
[komentar]
4. baris kosong
° Komentar:
; [Text]
° Huruf besar/kecil tidak dibedakan
11
Contoh Program
;***** Subroutine Register Variables
.def
A
=r13
.def
B
=r14
.def
cnt2
=r15
.def
cnt1
=r16
.def
endL
=r17
.def
endH
=r18
;***** Code
bubble:
mov
mov
mov
i_loop:
ld
ld
cp
brlo
st
std
L1:
dec
brne
dec
brne
ret
ZL,endL
ZH,endH
cnt2,cnt1
A,Z
B,-Z
A,B
L1
Z,A
Z+1,B
cnt2
i_loop
cnt1
bubble
;first value to be compared
;second value to be compared
;inner loop counter
;outer loop counter
;end of data array low address
;end of data array high address
;init Z pointer
;counter2 <- counter1
;get first byte, A (n)
;decrement Z and get second byte, B (n-1)
;compare A with B
;if A not lower
;store swapped
;end inner loop
;end outer loop
12
Directives
13
Peta Memori
Memori Program
Memori Data
° Program dan data ditempatkan pada memori yang
pengalamatannya terpisah
° Memori data mencakup Register, I/O, SRAM
Internal, SRAM Eksternal
14
CSEG, DSEG, ESEG
° The CSEG directive defines the start of a Code Segment
° An Assembler file can consist of several Code Segments,
which are concatenated into one Code Segment when
assembled
° The default segment type is Code
° Syntax:
.CSEG
° Example:
.DSEG
vartab:
; Start data segment
.BYTE 4
.CSEG
const:
; Reserve 4 bytes in SRAM
; Start code segment
.DW 2
; Write 0x0002 in prog.mem.
mov r1,r0
; Do something
15
ORG
° The ORG directive sets the location counter (within memory
segment) to an absolute value (as the parameter)
° If the directive is preceded by a label (on the same source
code line), the label will be given the value of the parameter
° The default values of the Code and EEPROM location
counters are zero, whereas the default value of the SRAM
location counter is 32 when the assembling is started
° Syntax:
.ORG
expression
° Example:
.DSEG
.ORG
variable:
.ESEG
.ORG
eevar:
.CSEG
.ORG
0x20
.DW 0xfeff
; Start data segment
; Set SRAM address to hex 67
; Reserve a byte at SRAM adr.67H
; Start EEPROM Segment
; Set EEPROM location counter
; Initialize one word
0x10
mov r0,r1
; Set Program Counter to hex 10
; Do something
0x67
.BYTE 1
16
BYTE
° The BYTE directive reserves memory resources in the SRAM
° In order to be able to refer to the reserved location, the BYTE
directive should be preceded by a label
° The directive can only be used within a Data Segment
° Syntax:
LABEL:
.BYTE expression
° Example:
.DSEG
var1:
.BYTE 1
; reserve 1 byte to var1
table:
.BYTE tab_size
; reserve tab_size bytes
ldi
r30,low(var1)
; Load Z register low
ldi
r31,high(var1)
; Load Z register high
ld
r1,Z
; Load VAR1 into register 1
.CSEG
17
DB, DW
° The DB directive reserves memory resources in the program
memory (CSEG) or the EEPROM (ESEG) memory
° The DB directive should be preceded by a label
° The DB directive takes a list of expressions, and must contain
at least one expression
° Each expression must evaluate to a number between -128 (2’s
complement) and 255
° Syntax:
LABEL:
.DB expressionlist
° Example:
.CSEG
consts:
.DB 0, 255, 0b01010101, -128, 0xaa
.ESEG
eeconst:
.DB 0xff
18
DEF
° The DEF directive allows the registers to be referred to
through symbols
° A defined symbol can be used in the rest of the program to
refer to the register it is assigned to
° A register can have several symbolic names attached to it
° A symbol can be redefined later in the program
° Syntax:
.DEF
Symbol=Register
° Example:
.DEF
.DEF
.CSEG
temp=R16
ior=R0
ldi temp,0xf0
in ior,0x3f
; Load 0xf0 into temp register
; Read SREG into ior register
eor temp,ior
; Exclusive or temp and ior
19
EQU
° The EQU directive assigns a value to a label
° This label can then be used in later expressions
° A label assigned to a value by the EQU directive is
a constant and can not be changed or redefined
° Syntax:
.EQU
label = expression
° Example:
.EQU
.EQU
io_offset = 0x23
porta = io_offset + 2
.CSEG
clr r2
out porta,r2
; Start code segment
; Clear register 2
; Write to Port A
20
SET
° The SET directive assigns a value to a label
° This label can then be used in later expressions
° A label assigned to a value by the SET directive can
be changed later in the program
° Syntax:
.SET
label = expression
° Example:
.SET
.SET
io_offset = 0x23
porta = io_offset + 2
.CSEG
clr r2
out porta,r2
; Start code segment
; Clear register 2
; Write to Port A
21
EXIT
° The EXIT directive tells the Assembler to stop
assembling the file
° Normally, the Assembler runs until end of file (EOF)
° Syntax:
.EXIT
° Example:
.EXIT
; Exit this file
22
MACRO, ENDMACRO
° The MACRO directive tells the Assembler that this is the start
of a Macro
° A Macro can take up to 10 parameters (referred to as @0-@9
within the Macro definition)
° The Macro definition is terminated by an ENDMACRO
directive
° Syntax:
.MACRO macroname
.ENDMACRO
° Example:
.MACRO
SUBI16
; Start macro definition
subi @1,low(@0)
; Subtract low byte
sbci @2,high(@0) ; Subtract high byte
.ENDMACRO
; End macro definition
.CSEG
; Start code segment
SUBI16 0x1234,r16,r17
; Sub.0x1234 from r17:r16
23
Expressions:
Operands, Operators, Functions
24
Operands
° Reminder:
1. [label:]
2. [label:]
directive
instruction
[operands]
[operands]
[komentar]
[komentar]
° User defined labels which are given the value of the
location counter at the place they appear
° User defined variables defined by the SET directive
° User defined constants defined by the EQU
directive
° Integer constants: constants can be given in
several formats, including
a) Decimal (default): 10, 255
b) Hexadecimal (two notations): 0x0a, $0a, 0xff, $ff
c) Binary: 0b00001010, 0b11111111
° PC (program counter) - the current value of the
Program memory location counter
25
Unary Operators
° Logical Not Symbol: !
• returns 1 if the expression was zero, and returns 0 if the expression
was nonzero
ldi r16,!0xf0
; Load r16 with 0x00
° Bitwise Not Symbol: ~
• returns the input expression with all bits inverted
ldi r16,~0xf0
; Load r16 with 0x0f
° Unary Minus Symbol: • returns the arithmetic negation of an expression
ldi r16,-2
; Load -2(0xfe) in r16
26
Binary Operators
° Multiplication Symbol: *
• returns the product of two expressions
ldi r30,label*2
; Load r30 with label*2
° Division Symbol: /
• returns the integer quotient of the left expression divided by the right
expression
ldi r30,label/2
; Load r30 with label/2
° Addition Symbol: +
• returns the sum of two expressions
ldi r30,c1+c2
; Load r30 with c1+c2
° Subtraction Symbol: • returns the left expression minus the right expression
ldi r17,c1-c2
;Load r17 with c1-c2
27
Binary Operators
° Shift left Symbol: <<
• returns the left expression shifted left a number of times given by the right
expression
Ldi r17,1<<bitmask ;Load r17 with 1 shifted left bitmask times
° Shift right Symbol: >>
• returns the left expression shifted right a number of times given by the right
expression.
ldi r17,c1>>c2
;Load r17 with c1 shifted right c2 times
° Less than Symbol: <
• returns 1 if the signed expression to the left is Less than the signed
expression to the right, 0 otherwise
ori r18,bitmask*(c1<c2)+1
;Or r18 with an expression
° Less or Equal Symbol: <=
• returns 1 if the signed expression to the left is Less than or Equal to the
signed expression to the right, 0 otherwise
ori r18,bitmask*(c1<=c2)+1 ;Or r18 with an expression
28
Binary Operators
° Greater than Symbol: >
• returns 1 if the signed expression to the left is Greater than the signed
expression to the right, 0 otherwise
ori r18,bitmask*(c1>c2)+1
;Or r18 with an expression
° Greater or Equal Symbol: >=
• returns 1 if the signed expression to the left isGreater than or Equal to the
signed expression to the right, 0 otherwise
ori r18,bitmask*(c1>=c2)+1 ;Or r18 with an expression
° Equal Symbol: ==
• returns 1 if the signed expression to the left is Equal to the signed expression
to the right, 0 otherwise
andi r19,bitmask*(c1==c2)+1;And r19 with an expression
° Not Equal Symbol: !=
• returns 1 if the signed expression to the left is Not Equal to the signed
expression to the right, 0 otherwise
.SET flag=(c1!=c2) ;Set flag to 1 or 0
29
Binary Operators
° Bitwise And Symbol: &
• returns the bitwise And between two expressions
ldi r18,High(c1&c2) ;Load r18 with an expression
° Bitwise Xor Symbol: ^
• returns the bitwise Exclusive Or between two expressions
ldi r18,Low(c1^c2)
;Load r18 with an expression
° Bitwise Or Symbol: |
• returns the bitwise Or between two expressions
ldi r18,Low(c1|c2)
;Load r18 with an expression
° Logical And Symbol: &&
• returns 1 if the expressions are both nonzero, 0 otherwise
ldi r18,Low(c1&&c2) ;Load r18 with an expression
° Logical Or Symbol: ||
• returns 1 if one or both of the expressions are nonzero, 0 otherwise
ldi r18,Low(c1||c2)
;Load r18 with an expression
30
Functions
° LOW(expression)
returns the low byte of an expression
° HIGH(expression)
returns the second byte of an expression
° BYTE2(expression)
is the same function as HIGH
° BYTE3(expression)
returns the third byte of an expression
° BYTE4(expression)
returns the fourth byte of an expression
° LWRD(expression)
returns bits 0-15 of an expression
° HWRD(expression)
returns bits 16-31 of an expression
° PAGE(expression)
returns bits 16-21 of an expression
° EXP2(expression)
returns 2 to the power of expression
° LOG2(expression)
returns the integer part of log2(expression)
31
AVR Studio
32
AVR Studio: Eksekusi Program
33
Inspeksi Status Prosesor
° Status Prosesor dapat dilihat pada window “Processor”:
34
Inspeksi Isi Register
° Isi Register dapat dilihat pada window “Register”:
35
Inspeksi Isi Memori
° Isi Memori dapat dilihat pada window “Memory”:
36