Chapter 7 – MSP430
Assembler / Linker
Concepts to Learn…












MSP430 Assembler
High Level vs. Assembly
Assembly Code
Assembly Process
MSP430 Assembler
Assembly Directives
Assembly Sections
Linker
Libraries
Code Composer Essentials/Studio
Systematic Decomposition
Device: LED’s
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
2
Moving Up Levels of Abstraction
Problems
Algorithms
Language
Assembly code
Machine (ISA) Architecture
Machine code
Micro-architecture
LC-3 Architecture
Circuits
Logic gates, multiplexers, memory, etc.
Devices
Transistors
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
3
Assembler
Assembler
An assembler outputs
an object file as input
to a linker program
An assembler
translates a program
into machine code
An assembly program
is a text file
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
4
High Level vs. Assembly
High Level vs. Assembly

High Level Languages




More programmer friendly
More ISA independent
Each high-level statement translates to several
instructions in the ISA of the computer
Assembly Languages





Lower level, closer to ISA
Very ISA-dependent
Each instruction specifies a single ISA instruction
Makes low level programming more user friendly
More efficient code
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
5
High Level vs. Assembly
Why Assembly Code?



Allows us to work at a slightly higher level than
machine language.
Allows us to use symbolic names for opcodes
Allows us to use symbolic names for memory
locations 




SUM, PRODUCT
Don’t need to know every address of every storage
location.
Calculates addresses for us – really a big deal!
Helps to allocate memory locations.
Provides additional error checking
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
6
Assembly Code
Assembly Code Example
;*******************************************************************************
;
CS/ECEn 124 Lab 4 - morse.asm: Student Code
;*******************************************************************************
.cdecls C,LIST, "msp430x22x4.h“
; include C header
COUNT
Labels
.equ
Instructions
2000
;-----------------------------------------------------------------------------.data
; data
.bss
cnt,2
; ISR counter
;-----------------------------------------------------------------------------.text
; Program reset
RESET:
mov.w
#0x0280,SP
; Initialize stack pointer
mov.w
#WDT_MDLY_0_5,&WDTCTL
; Set Watchdog interval to ~0.5ms
mov.b
#WDTIE,&IE1
; Enable WDT interrupt
bis.b
#0x01,&P1DIR
; P1.0 output
bis.b
#0x20,&P4DIR
; P4.0 output
mov.w
#COUNT,&cnt
; initialize counter
bis.w
#LPM0+GIE,SR
; Enter LPM0 w/ interrupt
jmp
$
; Loop forever; interrupts do all
;
;
WDT_ISR:
WDT_exit:
Directives
BYU CS/ECEn 124
Watchdog Timer interrupt service routine
xor.b
dec.w
jne
mov.w
xor.b
#0x20,&P4OUT
&cnt
WDT_exit
#COUNT,&cnt
#0x01,&P1OUT
reti
; pulse buzzer
; decrement counter
Comments
; initialize counter
; toggle P1.0
; return from interrupt
.sect
.word
".int10"
WDT_ISR
; MSP430 RESET Vector
; Watchdog ISR
.sect
.word
.end
".reset"
RESET
; MSP430 RESET Vector
; Power Up ISR
Chapter 7 - MSP430 Assembler
7
Assembly Code
Assembly Syntax


The MSP430 assembler reads up to 200 characters per
line. Any characters beyond 200 are truncated.
Follow these guidelines:





All statements must begin with a label, a blank, an asterisk, or a
semicolon
Labels are optional; if used, they must begin in column 1
One or more blanks must separate each field. Tab and space
characters are blanks.
Comments are optional. Comments that begin in column 1 can
begin with an asterisk or a semicolon (* or ;), but comments that
begin in any other column must begin with a semicolon.
A mnemonic cannot begin in column 1 or it will be interpreted as
a label
[label[:]]mnemonic [operand list][;comment]
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
8
Assembly Code
Assembly Syntax

Label Field








Labels are optional for all assembly language instructions and
for most (but not all) assembler directives
When used, a label must begin in column 1
A label can contain up to 128 alphanumeric characters (A-Z, a-z,
0-9, _, and $)
Labels are case sensitive and the first character cannot be a
number
A label can be followed by a colon (:). (If you do not use a label,
the first character position must contain a blank, a semicolon, or
an asterisk)
The value of a label is the current value of the Location Counter
A label on a line by itself is a valid statement
If you do not use a label, the character in column 1 must be a
blank, an asterisk, or a semicolon
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
9
Assembly Code
Assembly Syntax

Mnemonic Field




The mnemonic field follows the label field.
The mnemonic field cannot start in column 1; if it does, it is
interpreted as a label.
The mnemonic field can begin with one of the following items:




Machine-instruction mnemonic (such as ADD, MOV, JMP)
Assembler directive (such as .data, .list, .equ)
Macro directive (such as .macro, .var, .mexit)
Macro call
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
10
Assembly Code
Assembly Syntax

Operand Field



The operand field follows the mnemonic field and contains one
or more operands.
The operand field is not required for all instructions or directives.
An operand consists of the following items:






Symbols
Constants
Expressions (combination of constants and symbols)
You must separate operands with commas
You use immediate values as operands primarily with
instructions
Use the # prefix to define an immediate value
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
11
Assembly Code
Assembly Syntax

Constants



The assembler maintains constants internally as a 32-bit
quantities
Constants are not sign extended (ie, 00FFh is equal to 00FF
(base 16) or 255 (base 10); however, it does not equal -1 unless
a byte directive)
Types of constants:



Decimal: string of decimal digits ranging from (-2147483648 to
4294967295 (ie, 1000, -32768)
Hexadecimal: string of up to 8 hexadecimal digits followed by suffix
‘H’ (or ‘h’) or preceded by ‘0x’ (ie, 78h, 0x78)
Binary: string of upt to 32 binary digits followed by suffix B (or b) (ie.
0000b, 11110000B)
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
12
Assembly Code
Assembly Syntax

Expressions



An expression is a constant, a symbol, or a series of constants
and symbols separated by arithmetic operators.
The 32-bit ranges of valid expression values are -2147 483 648 to
2147 483 647 for signed values, and 0 to 4 294 967 295 for
unsigned values.
Three main factors influence the order of expression evaluation:

Parentheses Expressions enclosed in parentheses are always
evaluated first. (You cannot substitute braces ( { } ) or brackets ( [ ] )
for parentheses)


Precedence groups Operators: when parentheses do not determine
the order of expression evaluation, the highest precedence operation
is evaluated first.


8 / (4 / 2) = 4, but 8 / 4 / 2 = 1
8 + 4 / 2 = 10 (4 / 2 is evaluated first)
Left-to-right evaluation: when parentheses and precedence groups do
not determine the order of expression evaluation, the expressions are
evaluated from left to right
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
13
Assembly Code
Assembly Syntax

Operators can be used in expressions and are evaluated
according to precedence group
Group Operator
1
+, -, ~, !
2
3
4
5
*, /, %
+, <<, >>
<, <=, >, >=
6
7
8
9
=[=], !=
&
^
|
BYU CS/ECEn 124
Description
Unary plus, minus, 1’s complement,
Logical NOT
Multiplication, Division, Modulo
Addition, Subtraction
Shift left, Shift right
Less than, Less than or equal to, Greater
than, Greater than or equal to
Equal to, Not equal to
Bitwise AND
Bitwise exclusive OR (XOR)
Bitwise OR
Chapter 7 - MSP430 Assembler
14
Assembly Code
Assembler Directives

Assembly directives are used to specify:



Starting addresses for programs
Starting values for memory locations
Specify the end of program text.
;*******************************************************************************
;
CS/ECEn 124 Example Code
;*******************************************************************************
.cdecls C,LIST, "msp430x22x4.h“
; include C header
COUNT
Directives
.equ
;-----------------------------------------------------------------------------.data
; data
.bss
cnt,2
; ISR counter
;-----------------------------------------------------------------------------.text
; Program reset
RESET:
mov.w
#0x0280,SP
; Initialize stack pointer
mov.w
#WDT_MDLY_0_5,&WDTCTL
; Set Watchdog interval to ~0.5ms
bis.w
#LPM0+GIE,SR
; Enter LPM0 w/ interrupt
jmp
$
; Loop forever; interrupts do all
.sect
.word
.end
BYU CS/ECEn 124
2000
".reset"
RESET
; MSP430 RESET Vector
; Power Up ISR
Chapter 7 - MSP430 Assembler
15
Assembly Process
Assembly Process


The assembler translates assembly language
programs (.asm) into the machine language of the
ISA (.obj).
There is a 1-to-1 correspondence between
assembly language instructions and instructions in
the final machine language.
First Pass:

find all labels and their corresponding addresses
this information is stored in the symbol table
Second Pass:

convert instructions to machine language, using
information from symbol table
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
16
Assembly Process
1st Pass: Construct Symbol Table
1. Find the .text statement, which tells us the
address of the first instruction
a. Initialize location counter (LC)
b. Incremented for each new instruction
2. For each non-empty line in the program:
a. If line contains a label, add label and LC to symbol
table.
b. Increment LC (according to instruction length.)
1. All instructions are 1, 2, or 3 words in length
2. Some directives like .bss or .string increment LC by the
size of the operand.
3. Stop when .end statement is reached.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
17
Assembly Process
2nd Pass: Generate Machine Language
1. Reset location counter (LC)
2. For each executable assembly language
statement, generate the corresponding
machine language instruction.
a. resolve labels referenced in instructions using the
symbol table
b. increment LC for each instruction as on pass 1
c. output resulting machine code to output files
3. Stop when .end statement is reached.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
18
Assembly Process
Assembly Style Guidelines





Provide a program header, with author’s name, date, etc.,
and purpose of program.
Start labels, opcode, operands, and comments in same
column for each line. (Unless entire line is a comment.)
Use comments to explain what each register does.
Remember, the assembler is case sensitive.
Use meaningful symbolic names.
 Mixed upper and lower case for readability.
 ASCIItoBinary, InputRoutine, SaveR1


Provide comments between program sections.
Each line must fit on the page -- no wraparound or
truncations.
 Long statements split in aesthetically pleasing manner.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
19
MSP430 Assembler
MSP430 Assembler


The MSP430 assembler translates your source
code into machine language
Source files may contain the following elements:





Assembly directives
Macro directives
Assembly language instructions
For more detailed information on each element,
please refer to the MSP430 Assembly Language
Tools User’s Guide (slau131b.pdf)
Some of the most relevant aspects of the
assembly language for the MSP430 will now be
introduced
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
20
MSP430 Assembler
Stoplight Example
;*******************************************************************************
;
CS/ECEn 124 Lab 4 - stoplight.asm: Software Toggle P1.0
;*******************************************************************************
.cdecls C,LIST, "msp430x22x4.h" ; MSP430F2274
;-----------------------------------------------------------------------------.text
; beginning of executable code
;-----------------------------------------------------------------------------RESET:
mov.w
#0x0280,SP
; init stack pointer
mov.w
#WDTPW+WDTHOLD,&WDTCTL ; stop WDT
bis.b
#0x01,&P1DIR
; set P1.0 as output
mainloop:
xor.b
mov.w
#0x01,&P1OUT
#0,r15
; toggle P1.0
; use R15 as delay counter
delayloop:
dec.w
jnz
jmp
r15
delayloop
mainloop
; delay over?
; n
; y, toggle led
;-----------------------------------------------------------------------------;
Interrupt Vectors
;-----------------------------------------------------------------------------.sect
".reset"
; MSP430 RESET Vector
.short RESET
; start address
.end
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
21
MSP430 Assembler
MSP430 Assembler



The assembly programming tool processes the
source code, producing an object file, and a
descriptive listing of the entire process
This process is completely controlled by
macros, allowing conditional execution
The MPS430 source code programs contains
sequences of statements that have:




Assembly directives
Assembly instructions
Macros, and
Comments.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
22
MSP430 Assembler
Assembler Syntax

A line can have four fields


label, mnemonic, operand list, and comment
The general syntax is:
{label[:]} mnemonic {operand list} {;comment}

Some line examples are:
.sect ".sysmem“
var1
.word 2
.text
Label1: mov r4,r5
.end
BYU CS/ECEn 124
;
;
;
;
Data Space
variable var1 declaration
Program Space
move R4 contents to R5
Chapter 7 - MSP430 Assembler
23
MSP430 Assembler
Coding Guidelines

The general coding guidelines:






All statements must begin with a label, a blank, an
asterisk, or a semicolon
Labels are optional. If used, they must begin in
column 1
One or more blanks or tabs must separate each field
Comments are optional
Comments that begin in column 1 can begin with an
asterisk or a semicolon (* or ;), but comments that
begin in any other column must begin with a
semicolon
A mnemonic cannot begin in column 1 or it will be
interpreted as a label.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
24
MSP430 Assembler
Constants

The assembler supports several formats for
constants:






Binary integer: 11110000b
Octal integer: 226q
Decimal integer: 25
Hexadecimal integer: 078h
Character: a
Assembly time: value1
BYU CS/ECEn 124






Chapter 7 - MSP430 Assembler
0xf0
0x96
0x19
0x78
'a'
value1 .set 3
25
MSP430 Assembler
Symbols






Symbols are used as labels, constants, and
substitution symbols
A symbol name is a string of up to 200
alphanumeric characters (A-Z, a-z, 0-9, $, and _)
A symbol cannot contain embedded blanks and
the first character cannot be a number
Symbols are case sensitive
Symbols used as labels become symbolic
addresses that are associated with locations in
the program
Labels used locally within a file must be unique.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
26
Assembly Directives
Assembler Directives


Assembler directives supply data to the program
and control the assembly process
Assembler directives enable you to:








Assemble code and data into specified sections
Reserve space in memory for uninitialized variables
Control the appearance of listings
Initialize memory
Assemble conditional blocks
Define global variables
Specify libraries from which the assembler can obtain
macros
Examine symbolic debugging information.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
27
Assembler Directives
Section Assembler Directives

Assembler directives that define sections:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
28
Assembler Directives
Assembler Directives

Assembler directives that initialize constants
(data and memory):
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
29
Assembler Directives
Assembler Directives

Assembler directives that perform alignment and
reserve space:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
30
Assembler Directives
Assembler Directives

Assembler directives that format the output listing:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
31
Assembler Directives
Assembly List File

A line in a listing
file has four fields:




Field 1: contains
the source code
line counter
Field 2: contains
the section
program counter
Field 3: contains
the object code
Field 4: contains
the original source
statement.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
32
Assembler Directives
Assembler Directives

Assembler directives that reference other files:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
33
Assembler Directives
Assembler Directives

Assembler directives that enable conditional
assembly:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
34
Assembler Directives
Assembler Directives

Assembler directives that define structures:

Directives that define symbols at assembly time:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
35
Assembler Directives
Assembler Directives

Assembler directives that perform miscellaneous
functions:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
36
Assembler Sections
Assembler Sections




The smallest unit of an object file is called a
section
A section is a block of code or data that occupies
contiguous space in the memory map
Each section of an object file is separate and
distinct.
Object files contain three default sections:



.text section contains executable code
.data section contains initialized data
.bss section reserves space for uninitialized variables.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
37
Linker
Linker

Example: process of linking two files together:
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
38
Libraries
Library Routines

Library




A set of routines for a specific domain application.
Example: math, graphics, GUI, etc.
Defined outside a program.
Library routine invocation



Labels for the routines are defined as .def
Each library routine contains its own symbol table.
A linker resolves the external addresses before
creating the executable image.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
39
Libraries
Linking
multiple
files
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
40
Code Composer
Code Composer

Based on Eclipse framework



Allows integration with other compilers, plugins
One stop shop with TI


MSP430 + FET Programmer + CCE
Support




Open source enabling rapid innovation
Direct from TI
Eclipse Community
Third Parties
Low cost solution (Free!)
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
41
Code Composer
CCE Window – C/C++ Perspective
1-click project debug
Project View
• List of all Projects
Independent debugging
and Programming view
Project Outline
• Shortcut to all parts
of the project
Code Window
• Real-time
breakpoints
• Syntax highlighting
Problems View
• Information
• Warnings
• Errors
Console
Build information
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
42
Code Composer
CCE Window – Debug Perspective
1-click project debug
Target control
• Start, stop, halt
• Single stepping
• Stack trace
Independent debugging
and Programming view
Real-time, in-system
MSP430 information
• Register access
• Flash, RAM, Info
segment access
• Disassembly view
Code Window
• Real-time
breakpoints
• Syntax highlighting
Highly configurable
window layout
• User preferences
• Plugin support
Easy to view
program size info
CPU Cycle counter
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
43
Code Composer
The MSP430 Assembler

To create a new Assembly language project:





In File -> New Project choose Managed Make C/ASM
Project (Recommended)
Assign a name to the project in Project Name, (e.g.,
stoplight)
Choose Project Type: MSP430 Executable
In Additional Project Setting, do not choose any
connection with other projects
In the Device Selection page, select the target device



MSPF2013 or MSP430F2274
Select configuration option: Assembly only Project
At the end of this sequence of operations, a project
named stoplight is opened in the work environment
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
44
Code Composer
The MSP430 Assembler

Assembly project (continued):



Assign a new source code file to the project. In the
option Menu > File > Source File and create a new
file called stoplight.asm
In the project properties menu, set the entry point as
identified by the label start
This option is found on page Build C/C++ build >
MSP430 Linker V3.0 > Symbol Management >
Specify the program entry point for the output
model (-entry point).
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
45
Code Composer
The MSP430 Assembly Listing

To generate an assembly listing:





Project -> Properties
C/C++ Build -> Tool Settings -> MSP430 Compiler v3.x
Assembler Options:
Check Generate listing file (--asm_listing)
To define program entry point:





Project -> Properties
C/C++ Build -> Tool Settings -> MSP430 Linker v3.x
Symbol Management:
Specify the program entry point for the output model (-- entry point)
Enter the start label
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
46
Systematic Decomposition
Systematic Decomposition
IDEA
Step by Step Procedure

Finiteness


Definiteness


Each step is precisely stated.
Effective Computability

BYU CS/ECEn 124
Must terminate.
Each step can be carried out.
Chapter 7 - MSP430 Assembler
47
Systematic Decomposition
Stepwise Refinement


Also known as incremental development.
Start with problem statement:
“Write an assembler program for a traffic stop light.”

Decompose task into a few simpler subtasks.





Turn on the green LED for 5 seconds.
Blink the green LED on and off at 1 second intervals for
6 seconds (3 offs and 3 ons).
Blink the green LED on and off at 0.25 second intervals
for 4 seconds (8 offs and 8 ons).
And finally, turn the green LED off for 10 seconds.
Repeat the process of dividing into subtasks until
you get to the machine instruction level.
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
48
Systematic Decomposition
F2274 Stoplight Example
;*******************************************************************************
;
CS/ECEn 124 Lab 4 - stoplight.asm: Software Toggle P1.0
;*******************************************************************************
.cdecls C,LIST, "msp430x22x4.h" ; MSP430F2274
;-----------------------------------------------------------------------------.text
; beginning of executable code
;-----------------------------------------------------------------------------RESET:
mov.w
#0x0280,SP
; init stack pointer
mov.w
#WDTPW+WDTHOLD,&WDTCTL ; stop WDT
bis.b
#0x01,&P1DIR
; set P1.0 as output
mainloop:
xor.b
mov.w
#0x01,&P1OUT
#0,r15
; toggle P1.0
; use R15 as delay counter
delayloop:
dec.w
jnz
jmp
r15
delayloop
mainloop
; delay over?
; n
; y, toggle led
;-----------------------------------------------------------------------------;
Interrupt Vectors
;-----------------------------------------------------------------------------.sect
".reset"
; MSP430 RESET Vector
.short RESET
; start address
.end
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
49
Device: LED
LEDs


A light-emitting diode (LED) is a
semiconductor light source
When a diode is forward biased (switched
on), electrons are able to recombine with
holes within the device, releasing energy
in the form of photons
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
50
Device: LED
LEDs

6 LED’s on eZ430X Development Board







P1.0
P1.1
P2.6
P2.7
P3.3
P4.6
Red LED eZ430-RF2500
Green LED eZ430-RF2500
LED #1 (Green)
LED #2 (Orange)
LED #3 (Yellow)
LED #4 (Red)
Port bits must be enabled for output by writing a 1 to the
port direction register






bis.b
bic.b
bis.b
bis.b
bis.b
bis.b
BYU CS/ECEn 124
#0x03,&P1DIR
#0xc0,&P2SEL
#0x40,&P2DIR
#0x80,&P2DIR
#0x08,&P3DIR
#0x40,&P4DIR
; eZ430-RF2500 LED's
; select GPIO
; LED #1 (P2.6)
; LED #2 (P2.7)
; LED #3 (P3.3)
; LED #4 (P4.6)
Chapter 7 - MSP430 Assembler
51
Device: LED
LEDs

Turn LED off by writing a 0 to the port pin






#0x03,&P1OUT
#0x40,&P2OUT
#0x80,&P2OUT
#0x08,&P3OUT
#0x40,&P4OUT
; eZ430-RF2500 LED's
; LED #1 (P2.6)
; LED #2 (P2.7)
; LED #3 (P3.3)
; LED #4 (P4.6)
Turn LED on by writing a 1 to the port pin






bic.b
bic.b
bic.b
bic.b
bic.b
bis.b
bis.b
bis.b
bis.b
bis.b
#0x03,&P1OUT
#0x40,&P2OUT
#0x80,&P2OUT
#0x08,&P3OUT
#0x40,&P4OUT
; eZ430-RF2500 LED's
; LED #1 (P2.6)
; LED #2 (P2.7)
; LED #3 (P3.3)
; LED #4 (P4.6)
Toggle LED by XOR’ing a 1 to the port pin





xor.b
xor.b
xor.b
xor.b
xor.b
BYU CS/ECEn 124
#0x03,&P1OUT
#0x40,&P2OUT
#0x80,&P2OUT
#0x08,&P3OUT
#0x40,&P4OUT
; eZ430-RF2500 LED's
; LED #1 (P2.6)
; LED #2 (P2.7)
; LED #3 (P3.3)
; LED #4 (P4.6)
Chapter 7 - MSP430 Assembler
52
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
53
Most Commonly Used Directives
Mnemonic and Syntax
Description
.bss symbol, size in bytes[, alignment]
Reserves size bytes in the .bss (uninitialized data) section
.data
Assembles into the .data (initialized data) section
.sect " section name"
Assembles into a named (initialized) section
.text
Assembles into the .text (executable code) section
.byte value1[, ..., valuen]
Initializes one or more successive bytes in the current section
.char value1[, ..., valuen]
Initializes one or more successive bytes in the current section
.string {expr1|"string1"}[,... , {exprn|"stringn"}]
Initializes one or more text strings
.word value1[, ... , valuen]
Initializes one or more 16-bit integers
.align [size in bytes]
Aligns the SPC on a boundary specified by size in bytes, which must be a power of 2; defaults to word (2 byte)
.title " string "
Prints a title in the listing page heading
.def symbol1[, ... , symboln]
Identifies one or more symbols that are defined in the current module and that can be used in other modules
.include ["]filename["]
Includes source statements from another file
.ref symbol1[, ... , symboln]
Identifies one or more symbols used in the current module that are defined in another module
.else
Assembles code block if the .if well-defined expression is false. (Optional)
.elseif well-defined expression
Assembles code block if the .if well-defined expression is false and the .elseif condition is true. (Optional)
.endif
Ends .if code block
.if well-defined expression
Assembles code block if the well-defined expression is true
symbol .equ value
Equates value with symbol
symbol .set value
Equates value with symbol
.cdecls [options,] "filename"[, "filename2"[, ...]
Share C headers between C and assembly code
.end
Ends program
BYU CS/ECEn 124
Chapter 7 - MSP430 Assembler
54