What is an Assembler? An assembler is a program that translates symbolic code (assembly language) into executable object code. This object code can be executed with a 80C5!compatible microcontroller. "# you ha$e e$er written a computer program directly in machine!recogni%able #orm& such as binary or hexadecimal code& you will appreciate the ad$antages o# programming in symbolic assembly language. Assembly language operation codes (mnemonics) are easily remembered ('#or mo$e instructions& A** #or addition& and so on). +ou can also symbolically express addresses and $alues re#erenced in the operand #ield o# instructions. ,ecause you assign these names& you can ma-e them as meaning#ul as the mnemonics #or the instructions. or example& i# your program must manipulate a date as data& you can assign it the symbolic name *AT/. "# your program contains a set o# instructions used as a timing loop (executed repeatedly until a speci#ic amount o# time has passed)& you can name the instruction group T"'/123 . An assembly program has three parts4 'achine instructions ! Code the machine can execute. *etailed discussion o# the machine instructions is in the hardware manuals o# the 80C5microcontroller. Assembler directi$es ! *e#ine the program structure and symbols& and generate non executable code (data& messages& and so on.). Assembler controls ! et assembly modes and direct assembly #low. Un ensamblador es un programa que traduce el código simbólico (lenguaje ensamblador) en código objeto ejecutable. Este código objeto puede ser ejecutado con un microcontrolador 80C51-compatible. i alguna !e" #a escrito un programa de ordenador directamente en la m$quina de %orma reconocible& como código binario o #e'adecimal& apreciar$n las !entajas de la programación en lenguaje ensamblador simbólico. En el lenguaje sembler los códigos de las operación (mnemotcnicos) son %$ciles de recordar (*+, para las instrucciones de mo!er& para la suma& as/ sucesi!amente). ambin puede e'presar simbólicamente las direcciones los !alores de re%erencia en los operando en el campo de las instrucciones. ebido a que asigne estos nombres& se puede #acer como signi%icati!a como los mnemotcnicos para las instrucciones. or ejemplo& si tu programa debe manipular una %ec#a como datos& puede asignarle el nombre simbólico 2EC3. i el programa contiene un conjunto de instrucciones utili"ado como un calendario de bucle (ejecutado !arias !eces #asta una determinada cantidad de tiempo que #a pasado)& usted puede nombrar a la instrucción grupo 4*E67++. Un programa en asembler tiene tres partes• 4nstrucciones de m$quina - Código de la m$quina puede se ejecutado. etallada e'plicación de instrucciones de m$quina est$ en los manuales #ard9are del 80C51 microcontrolador. • ssembler directi!as - e%inir la estructura de los ♣programas los s/mbolos& no generar código ejecutable (datos& mensajes& etc.). • ssembler controles : 2ija los modos del ensamblador.
An assembler is a program that translates symbolic code (assembly language) into executable objectcode. This object code can be executed with a 80C5!compatible microcontroller. "# you ha$e e$erwritten a computer program directly in machine!recogni%able #orm& such as binary or hexadecimal
code& you will appreciate the ad$antages o# programming in symbolic assembly language.
Assembly language operation codes (mnemonics) are easily remembered (' #or mo$e instructions&A** #or addition& and so on). +ou can also symbolically express addresses and $alues re#erenced inthe operand #ield o# instructions. ,ecause you assign these names& you can ma-e them as meaning#ulas the mnemonics #or the instructions. or example& i# your program must manipulate a date as data&you can assign it the symbolic name *AT/. "# your program contains a set o# instructions used as atiming loop (executed repeatedly until a speci#ic amount o# time has passed)& you can name theinstruction group T"'/123.
An assembly program has three parts4
'achine instructions ! Code the machine can execute. *etailed discussion o# the machine
instructions is in the hardware manuals o# the 80C5 microcontroller.
Assembler directi$es ! *e#ine the program structure and symbols& and generate non
executable code (data& messages& and so on.).
Assembler controls ! et assembly modes and direct assembly #low.
Un ensamblador es un programa que traduce el código simbólico (lenguajeensamblador) en código objeto ejecutable. Este código objeto puede serejecutado con un microcontrolador 80C51-compatible. i alguna !e" #a escritoun programa de ordenador directamente en la m$quina de %orma reconocible& como
código binario o #e'adecimal& apreciar$n las !entajas de la programación enlenguaje ensamblador simbólico.
En el lenguaje sembler los códigos de las operación (mnemotcnicos) son%$ciles de recordar (*+, para las instrucciones de mo!er& para la suma& as/ sucesi!amente). ambin puede e'presar simbólicamente las direcciones los !alores de re%erencia en los operando en el campo de las instrucciones.ebido a que asigne estos nombres& se puede #acer como signi%icati!a como losmnemotcnicos para las instrucciones. or ejemplo& si tu programa debemanipular una %ec#a como datos& puede asignarle el nombre simbólico 2EC3. iel programa contiene un conjunto de instrucciones utili"ado como un calendariode bucle (ejecutado !arias !eces #asta una determinada cantidad de tiempo que#a pasado)& usted puede nombrar a la instrucción grupo 4*E67++.
Un programa en asembler tiene tres partes• 4nstrucciones de m$quina - Código de la m$quina puede se
ejecutado. etallada e'plicación de instrucciones de m$quina est$en los manuales #ard9are del 80C51 microcontrolador.
• ssembler directi!as - e%inir la estructura de los♣ programas los s/mbolos& no generar código ejecutable (datos& mensajes&etc.).
• ssembler controles : 2ija los modos del ensamblador.
Assembly program source #iles are made up o# statements that may include controls&
assembler control statements& or 805 'C9 instructions (mnemonics). or example4
;47E(emo rogram <1)
CE= 0000#
>* ;
E?
This example program consists o# #our statements. $TITLE is a directi$e& CSEG and END
are control statements& and JMP is an 805 'C9 instruction.
Each line o an assembly !ro"ram can contain only one #irectie% controlstatement% or MC& instr'ction( Statements m'st be containe# in e)actly one line(M'lti*line statements are not allo+e#.
Statements in ),- assembly !ro"rams are not col'mn sensitie( Directies% controlstatements% or MC& instr'ctions may start in any col'mn( "ndentation used in the
examples in this manual is done #or program clarity and is neither re:uired nor expected bythe assembler. The only exception is that arguments and instruction operands must be
separated #rom directi$es& control statements& or 'C9 instructions by at least one space.
All ),- assembly !ro"rams m'st incl'#e the END control statement( This control
statement signals to the assembler that this is the end o# the assembly program. Any 'C9
instructions& directi$es& or control statements #ound a#ter the END control statements areignored. The shortest $alid assembly program contains only an END control statement.
Assembler controls instruct the assembler how to process subse:uent assembly language
instructions. Controls also pro$ide a way #or you to de#ine program constants and reser$espace #or $ariables.
Assembler controls direct the operation o# the assembler when generating a listing #ile orobject #ile. Typically& controls do not impact the code that is generated by the assembler.
Controls can be speci#ied on the command line or within an assembler source #ile.
The conditional assembly controls are the only assembler controls that will impact the code
that is assembled by the A),- assembler. The I.& ELSE& ENDI.& and ELSEI. assemblercontrol statements pro$ide a power#ul set o# conditional operators that can be used to
include or exclude certain parts o# your program #rom the assembly.
The topic Control tatements describes the a$ailable assembler controls in detail andpro$ides an example o# each. e#er to this topic #or more in#ormation about control
Assembly language instructions speci#y the program code that is to be assembled by the
A),- assembler. The A),- assembler translates the assembly instructions in your programinto machine code and stores the resulting code in an object #ile.
Assembly instructions ha$e the #ollowing general #ormat4
@ label A mnemonic @ operand A @ & operand A @ B& operand A @ comment A
Where
label symbol name that is assigned the address at which the instruction is located.
mnemonic is the AC"" text string that symbolically represents a machine language
instruction.
operand is an argument that is re:uired by the speci#ied mnemonic .
comment is an optional description or explanation o# the instruction. A comment maycontain any text you wish. Comments are ignored by the assembler.
e#er to the x5 microcontrollers 805 "nstruction et 'anual& where they are listed by
mnemonic and by machine language opcode& #or more in#ormation about assemblerinstructions.
Comments are lines o# text that you may include in your program to identi#y and explain the
program. Comments are ignored by the A),- assembler and are not re:uired in order to
generate wor-ing programs.
+ou may include comments anywhere in your assembler program. Comments must be
preceded with a semicolon character (;). A comment can appear on a line by itsel# or canappear at the end o# an instruction. or example4
#is is a comment
?+ #is is also a comment
hen the assembler recogni%es the semicolon character on a line& it ignores subse:uenttext on that line. Anything that appears on a line to the right o# a semicolon will be ignored
by the A),- assembler. Comments ha$e no impact on object #ile generation or the codecontained therein.
Symbols an# Symbol Names6ome 7 riting Assembly 3rograms 7 ymbols and ymbol <ames
A symbol is a name that you de#ine to represent a $alue& text bloc-& address& or registername. +ou can also use symbols to represent numeric constants and expressions.
Symbol Names
ymbols are composed o# up to = characters #rom the #ollowing list4
A >& a %& 0 ?& 1& and @
A symbol name can start with any o# these characters except the digits 0 ?.
ymbols can be de#ined in a number o# ways. +ou may de#ine a symbol to represent anexpression using the E/& or SET control statements4
?U*DE624,E EU 5
UE627= E 1
27E627= E 0
+ou may de#ine a symbol to be a label in your assembly program4
7DE71 >?F 0& 7DE71
+ou can de#ine a symbol to re#er to a $ariable location4
E476DU22E GG#
ymbols are used throughout assembly programs. A symbolic name is much easier to
understand and remember than an address or numeric constant. The #ollowing topics
pro$ide more in#ormation about how to use and de#ine
A label de#ines a place (an address) in your program or data space. All rules that apply tosymbol names also apply to labels. hen de#ined& a label must be the #irst text #ield in a
line. "t may be preceded by tabs or spaces. A colon character (4) must immediately #ollowthe symbol name to identi#y it as a label. nly one label may be de#ined on a line. or
example4
7DE71 H
7DE7H label b itsel%
?U*DE D HI& JJ& K4?=K& 0 label at a message
C+L *+, M& <1H3 label in a program
"n the abo$e example& 2A,/2& 2A,/2B& <9',/& and C3+ are all labels.
hen a label is de#ined& it recei$es the current $alue o# the location counter o# the currently
selected segment. e#er to 2ocation Counter #or more in#ormation about the locationcounter.
+ou may use a label just li-e you would use a program o##set within an instruction. 2abelscan re#er to program code& to $ariable space in internal or external data memory& or can
re#er to constant data stored in the program or code space.
+ou may use a label to trans#er program execution to a di##erent location. The instruction
immediately #ollowing a label can be re#erenced by using the label. +our program can jumpto or ma-e a call to the label. The code immediately #ollowing the label will be executed.
+ou may use labels to pro$ide in#ormation to simulators and debuggers. A simulator ordebugger can pro$ide the label symbols while debugging. This can help to simpli#y the
debugging process.
2abels may only be de#ined once. They may not be rede#ined.
The Ax5 assembler maintains a location counter #or each segment which contains theo##set o# the instruction or data being assembled. The location counter increments a#ter
each line by the number o# bytes o# code or data in that line.
The location counter is initiali%ed to 0 #or each segment& but may be changed using the 01Gstatement.
The dollar sign character (D) may be used in an expression to obtain the current $alue o#
the location counter. or example& the #ollowing uses the location counter to determine thelength o# a string.
perands are arguments& or expressions& that are speci#ied along with assembler directi$es
or instructions. Assembler directi$es re:uire operands that are constants or symbols. orexample4
,,, EU J
10#
Assembler instructions support a wider $ariety o# operands than do directi$es. ome
instructions re:uire no operands and some may re:uire up to = operands. 'ultiple operandsare separated by commas. or example4
*+, H& <0
The number o# operands that are re:uired and their types depend on the instruction or
directi$e that is speci#ied. "n the #ollowing table& the #irst #our operands can also beexpressions. "nstruction operands can be classi#ied as one the #ollowing types4
0!eran# Ty!e Descri!tion
"mmediate *ata ymbols or constants the are used as an numeric $alue.
*irect ,it Address ymbols or constants that re#erence a bit address.
3rogram Addresses ymbols or constants that re#erence a code address.
*irect *ata Addresses ymbols or constants that re#erence a data address.
"ndirect Addresses "ndirect re#erence to a memory location& optionally with o##set.
The Ax5 assembler de#ines and reser$es names o# the ),- register set. These prede#ined
names are used in ),- programs to access the processor registers. ollowing& is a list o# theeach o# the 805& 80C5'E& and B5 registers along with a brie# description4
1e"ister Descri!tion
A epresents the 805 Accumulator. "t is used with many operations including
multiplication and di$ision& mo$ing data to and #rom external memory& ,ooleanoperations& etc.
DPT1 The *3T register is a F bit data pointer used to address data in E*ATA or
C*/ memory.
PC The 3C register is the F bit program counter. "t contains the address o# the
An immediate data operand is a numeric expression that is encoded as a part o# themachine language instruction. "mmediate data $alues are used literally in an instruction to
change the contents o# a register or memory location. The pound (or number) sign (I) mustprecede any expression that is to be used as an immediate data operand. The #ollowing
shows some examples o# how the immediate data is typically used4
"ndirect memory accesses uses the content o# a register in the instruction that reads orwrites into the memory. ith indirect address operands it is possible to access all memory
classes o# the A5.
The examples in *ATA and ,"T show how to access the di##erent memory classes o# an A5
'emory locations in the memory class *ATA can be addressed with both direct and indirect
memory accesses. pecial unction egisters () o# the A5 ha$e addresses abo$e 0x80in the *ATA memory class. locations can only be addressed with direct memory
accesses. An indirect memory access to s is not supported in the A5 microcontrollers.
E)am!le or all 53,- ariants
PPm!ar E=*E? de%ine a E=*E? o% class
E= PPm!ar,7UE 1 reser!e 1 DLE in space
4+6+H 003 special %unction register
,7UEH H03 absolute memor location
PPmprog E=*E? C+E de%ine a segment %or program code
'emory locations in the memory class ,"T are addressed with the bit instructions o# the
805. The pecial unction egisters () that are located in bit!addressable memorylocations can be addressed with bit instructions. ,it!addressable locations are4 806&
The /*ATA memory is only a$ailable in the <E3 80C5'E.
"n the <E3 80C5'E& the /*ATA memory can be accessed $ia /3T or the 9ni$ersal3ointers 30 and 3. 9ni$ersal 3ointers can access any memory location in the F',address space.
E)am!le or N6P 53C,-M6
PEPm6seg E=*E? E de%ine a E=*E? o% class E
E= PEPm6seg
4?= 100 reser!e 100 Dtes
PPmprog E=*E? C+E de%ine a segment %or program code
The E*ATA memory class can be accessed with the instruction 'E $ia the register *3T.A single page o# the E*ATA memory can be also accessed $ia the registers 0& . At the C
Compiler le$el this memory type is called !#ata and the segment pre#ix @3*@ is used. Thehigh address #or this pdata page is typically set with the 3B register. ,ut in new 805
$ariants there are also dedicated special #unction registers that de#ine the E*ATA pageaddress.
E)am!le or all 53,- ariants
POPm6seg E=*E? O de%ine a E=*E? o% class O
E= PEPm6seg
ODU22E 100 reser!e 100 Dtes
PPm!ars E=*E? O 4?=E de%ine a paged O segment
E= PPm!ars
,1 1 reser!e 1 bte
PPmprog E=*E? C+E de%ine a segment %or program code
3rogram addresses are absolute or relocatable expressions with the memory class C*/ or
/C*/. Typically& program addresses are used in jump and call instructions. or indirect jumps or calls& it is re:uired to load a program address in a register or a jump table. The
SJMP J7 JN7 8 1elatie 9'm!s include conditional jumps (CJNE% DJN7% J2% J2C%JC& J) and the unconditional SJMP instruction. The addressable
o##set is KB8 to LBG bytes #rom the #irst byte o# the instruction
that #ollows the relati$e jump. hen you use a relati$e jump inyour code& you must use an expression that e$aluates to the code
address o# the jump destination. The assembler does all the o##setcomputations. "# the address is out o# range& the assembler will
issue an error message.
ACALL AJMP In:bloc; 9'm!s an# calls permit access only within a BM,yte
bloc- o# program space. The low order bits o# the programcounter are replaced when the jump or call is executed. or *allas
=?0 contiguous mode the bloc- si%e is 5BM, or ? bits. "# ACALL or AJMP is the last instruction in a bloc-& the high order bits o# the
program counter change and the jump will be within the bloc-#ollowing the ACALL or AJMP.
LCALL LJMP Lon" 9'm!s an# calls allow access to any address within aFNM,yte segment o# program space. The low order F bits o# theprogram counter are replaced when the jump or call is executed.
or *allas =?0 contiguous mode4 the bloc- si%e is F', or BN bits.n <E3 80C5'E4 i# LCALL or LJMP is the last instruction in a
FNM,yte segment& the high order bits o# the program counterchange and the jump will into the segment #ollowing the LCALL or
LJMP.
ECALL EJMP E)ten#e# 9'm!s an# calls allow access within the extended
program space o# the <E3 80C5'E.
CALL JMP Generic 9'm!s an# calls are two instruction mnemonics that do
not represent a speci#ic opcode. JMP may assemble to SJMP%
AJMP% LJMP or EJMP. CALL may assemble to ACALL% LCALL orECALL. These generic mnemonics always e$aluate to aninstruction& not necessarily the shortest& that will reach the
speci#ied program address operand.
E)am!le or all 53,- <ariants
EO? C+E (m6%unction)
CE= J
>* e't6int an interrupt !ector
PPmintr E=*E? C+E de%ine a segment %or program code
E= PPmintr
e't6int >D 27=&%lag6+
4?C m6!ar
%lag6+ C7 27=
E4
PPmprog E=*E? C+E 4?D7+C a segment 9it#in a H blocV
An operand may be a numeric constant& a symbolic name& a character string or an
expression.
perators are used to combine and compare operands within your assembly program.
perators are not assembly language instructions nor do they generate A5 assembly code.They represent operations that are e$aluated at assembly time. There#ore& operators can
only handle calculations o# $alues that are -nown when the program is assembled.
An expression is a combination o# numbers& character string& symbols& and operators that
e$aluate to a single =B bit binary number (#or A54 F!bit binary number). /xpressions aree$aluated at assembly time and can& there#ore& be used to calculate $alues that would
otherwise be di##icult to determine be#orehand.
The #ollowing topics describe operators and expressions and how they are used in A5
<umbers may be speci#ied in hexadecimal (base F)& decimal (base 0)& octal (base 8)& and
binary (base B). The de#ault representation is decimal. A decimal& octal& or binary numbers
#irst character must always be a digit (0!?). 6exadecimal numbers whose #irst character isnot a digit (0!?) must be pre#ixed with a %ero (0).
The base o# a number is speci#ied by the last character in the number. A number that isspeci#ied without an explicit base is interpreted as decimal number.
The #ollowing table illustrates $arious types o# numbers4
AC"" characters may be used in an expression to generate numeric $alues. /xpressionsmay ha$e up to two AC"" characters enclosed in single :uotes (). 'ore than two
characters in an expression causes an error. ollowing are se$eral examples4
E)!ression <al'e
A 00Nh
A, NNBh
a 00Fh
ab FFBh
/rror4 <ull string is in$alid.
A,C /rror4 'ore than B characters.
Characters may be used anywhere in your program as a immediate data operand. orexample4
6ome 7 riting Assembly 3rograms 7 /xpressions and perators 7 Character trings
Character strings can be used in combination with the D2 assembler statement to de#inemessages that are used in your Ax5 assembly program. Character strings must be
enclosed within single :uotes (). or example4
EL*= D Kress an Ve to continue.K
generates the hexadecimal data (50h& GBh& F5h& G=h& G=h& B0h& J F/h& G5h& F5h& B/h)
starting at >EMSG. +ou can mix string and numeric data on the same line. orexample4
E+7*= D KEnd o% lineK& 00#
appends the $alue 00h to the end o# the string En# o line.
Two successi$e single :uote characters can be used to insert a single :uote into a string.
The Ax5 assembler maintains a location counter #or each segment which contains the
o##set o# the instruction or data being assembled. The location counter increments a#tereach line by the number o# bytes o# code or data in that line.
The location counter is initiali%ed to 0 #or each segment& but may be changed using the01G statement.
The dollar sign character (D) may be used in an expression to obtain the current $alueo# the location counter. or example& the #ollowing uses the location counter to
perators may be unary (re:uiring one operand) or binary (re:uiring two operands). The
combination o# an operator and its operand(s) is an expression. 3arentheses may be used inexpressions with multiple operators to speci#y the order in which operators are e$aluated. "#
no parentheses are used in an expression& operator precedence determines the e$aluationorder.
The Ax5 Assembler pro$ides a number o# control statements that permit you to de#ine
symbol $alues& reser$e and initiali%e storage& and control the placement o# your code.
These statements should not be con#used with processor instructions or with assemblerdirecti$es. They do not produce executable code and& with the exception o# the *,& **& and
* statements& they ha$e no direct e##ect on the contents o# code memory. These controlschange the state o# the assembler& de#ine user symbols& and add in#ormation to the object
#ile.
Control statements may be di$ided into the #ollowing categories4
A##ress Control
Statement Descri!tion
E<EN orces the location counter to the next e$en address.
01G ets the location counter to a speci#ies o##set or address.
&SING peci#ies which register ban- to use.
Con#itional Assembly
Statement Descri!tion
I. ,egins an I.:ELSE:ENDI. bloc-.
ELSEI. ,egins an alternate I. bloc-.
ELSE,egins an
ELSE bloc-.
ENDI. Terminates an I. bloc-.
Memory Initialiation
Statement Descri!tion
D2 Allocates memory #or one or more de#ined byte $alues.
DD Allocates memory #or one or more de#ined double word $alues.
DW Allocates memory #or one or more de#ined word $alues.
Symbols an# Symbol Names6ome 7 riting Assembly 3rograms 7 ymbols and ymbol <ames
A symbol is a name that you de#ine to represent a $alue& text bloc-& address& or register
name. +ou can also use symbols to represent numeric constants and expressions.
Symbol Names
ymbols are composed o# up to = characters #rom the #ollowing list4
A >& a %& 0 ?& 1& and @
A symbol name can start with any o# these characters except the digits 0 ?.
ymbols can be de#ined in a number o# ways. +ou may de#ine a symbol to represent an
expression using the E/& or SET control statements4
?U*DE624,E EU 5UE627= E 1
27E627= E 0
+ou may de#ine a symbol to be a label in your assembly program4
7DE71 >?F 0& 7DE71
+ou can de#ine a symbol to re#er to a $ariable location4
E476DU22E GG#
ymbols are used throughout assembly programs. A symbolic name is much easier tounderstand and remember than an address or numeric constant. The #ollowing topics
pro$ide more in#ormation about how to use and de#ine symbols.
Labels
Labels are special cases of symbols. Labels are used only before statements that
have physical addresses associated with them.
Examples of such statements are assembly language instructions, data storage
directives (DB and DW, and data reservation directives (D! and DB"#. Labels must
follow all the rules of symbol creation with the additional re$uirement that they be
followed by a colon. #he following are legal examples of label uses%
The Ax5 Assembler pro$ides a number o# directi$es you may use to control source #ile assembly.*irecti$es are composed o# one or more letters or digits and& unless otherwise speci#ied& may bespeci#ied a#ter the #ilename on the command line or within the source #ile when preceded by a dollarsign (D). or example4
51 *7E.51 L*D+7 EDU=
or
;L*D+7 EDU=
or
;L*D+7
;EDU=
The source #ile to assemble is A'32/.A5 and SM20LS and DE2&G are the directi$es.
Assembler directi$es may be di$ided into two groups4
Primary #irecties are speci#ied on the assembler command line or in #irst #ew lines o# the
assembly source #ile. These directi$es control how the assembler beha$es #or the entire
module. "# con#licting primary directi$es are speci#ied on the command line and in the source#ile& the command line directi$e ta-es precedence.
General #irecties may be speci#ied on the command line or anywhere in the source #ile.
These directi$es control the immediate beha$iour o# the assembler and may be changedduring assembly.
Note
yntax is the same #or directi$es speci#ied on the command line and those speci#ied in the
source #ile.
ome directi$es may not be speci#ied on the command line. "# one o# these directi$es isspeci#ied on the command line& the assembler generates a #atal error and aborts.
The #ollowing table is an alphabetical list o# the control directi$es a$ailable in the Ax5 Assembler.
Descri!tion The 01G statement alters the location counter #or the current segment and sets a
new origin #or subse:uent statements. The expression must be a simplerelocatable expression with no #orward re#erences. nly absolute addresses orsymbol $alues in the current segment may be used. The dollar!sign character (D)&which represents the current $alue o# the location counter& may be used in theexpression.
hen the 01G statement is encountered& the assembler calculates the $alue o# theexpression and changes the location counter.
"# the 01G statement appears in an absolute segment& the location counteris assigned the absolute address $alue speci#ied. The location counter maynot be set to an address below the base address o# the segment.
"# the 01G statement appears in a relocatable segment& the location
counter is assigned the o##set o# the speci#ied expression. or example& i#the relocatable segment starts at address 000h and i# the 01G
expression has a $alue o# B=Nh& the absolute address o# the nextstatement is BB=Nh (000h L B=Nh).
The 01G statement changes the location counter& which may create a gap& butdoes not create a new segment.
Note
"t is possible to use the 01G statement to change the location counter and
o$erwrite (or o$erlay) existing code or data. This is supported because o#legacy programs that used this techni:ue to de#ine multiple $ariables at thesame physical address. <o warning is generated i# the 01G statement isused this way.
Descri!tion The &SING statement speci#ies the register ban- (0!=) expression to use #or
encoding the A13:A14 registers. The register ban- selected is noted in theobject #ile and the memory area is reser$ed by the lin-er.
ome 805 instructions (li-e P&SB and P0P) allow only absolute addresses to be
used. The assembler replaces absolute registers (A13:A14) with the physicaladdress o# the register in the current register ban-. o& while the instruction P&SB13 is not $alid& P&SB A13 is $alid. 6owe$er& the assembler must -now whichregister ban- is used so that the correct physical address is calculated. This is thepurpose #or the &SING statement.
The &SING statement does not generate any code to switch the current register
ban-. The assembler program must select the correct register ban-. or example&the #ollowing code selects register ban- B4
U3 N sa!e t#e current register banV
*+, N& <(H 37 J) set register banV H
.
.
.
+ N restore sa!ed register banV
The physical address is calculated as #ollows4
@re"ister ban; 5 re"ister
Note
/xercise caution when using the E/& statement to de#ine a symbol #or an
absolute register (A13:A14). hen using E/&& the symbol $alue iscalculated at the time it is de#ined (not when it is used). "# the registerban- is subse:uently changed with the &SING statement& the de#inedsymbol will ha$e the incorrect address and the code generated is li-ely to#ail.
Synta) @ label A DB expression @ & expression ... A
Descri!tion The D2 statement initiali%es memory with one or more byte $alues. label is a
symbol that is assigned the current memory address. expression is a byte $aluethat is stored in memory. /ach expression may be a symbol& a string& or anexpression.
The D2 statement may be speci#ied only within a code or const segment. An erroris generated i# it is used in a di##erent segment.
n The DS statement reser$es the speci#ied number o# bytes in the current memoryspace. label is a symbol that is assigned the current memory address. expression isthe number o# bytes to reser$e.
This statement reser$es space and increments the location counter by the numbero# bytes reser$ed.
The E6T1N statement (which may appear anywhere in the assembler source #ile)speci#ies symbol s that the current source #ile uses but which are de#ined in otherobject modules. The module where the symbol s are de#ined must export them usinga P&2LIC statement.
alid classes are4
class Descri!tion
2IT A symbol located in ,"T memory space.
C0DE A symbol located in C*/ space.
DATA A symbol located in *ATA space.
IDATA A symbol located in "*ATA memory.
6DATA A symbol located in E*ATA memory.
N&M2E1 A symbol located in any memory space.
The lin-er resol$es all external symbols and $eri#ies that the classes and typesmatch. ymbols whose class is N&M2E1 match any memory class.
Synta) @ label A DW expression @ & expression ... A
Descri!tion The DW statement initiali%es memory with one or more word (B!byte) $alues. label
is a symbol that is assigned the current memory address. expression is a word$alue that is stored in memory. /ach expression may be a symbol& a string& or anexpression.
The DW statement may be speci#ied only within a code or const segment. An erroris generated i# it is used in a di##erent segment.
Descri!tion The 2SEG statement selects an absolute segment within ,"T space.
"# the optional address is included& the assembler starts the absolute segment #romthat address. The $alid address range is B0h!Bh.
"# the optional address is omitted& the assembler starts the absolute segment #romaddress 0 (i# no prior absolute ,"T segment was de#ined). "# an absolute ,"T segmentwas pre$iously de#ined& the assembler continues #rom the end o# that segment.
Note
The start address must be an absolute expression.
The AE5 Assembler con$erts ,/H statements into the #ollowing4
PD4PmodulenamePn E=*E? +22 address
Where
modulename is the name o# the source #ile.
n is a se:uential number.
address is the address speci#ied in the ,/H statement.
See Also 2IT& CSEG& DSEG& ISEG& 6SEG
E)am!le DE= 10 absolute D4 segment at 0'H0S10 bits R
Descri!tion The CSEG statement selects an absolute segment within C*/ space.
"# the optional address is included& the assembler starts the absolute segment #rom thataddress. The $alid address range is 0000h!0h.
"# the optional address is omitted& the assembler starts the absolute segment #romaddress 0 (i# no prior absolute C*/ segment was de#ined). "# an absolute C*/segment was pre$iously de#ined& the assembler continues #rom the end o# thatsegment.
Note
The start address must be an absolute expression.
The AE5 Assembler con$erts C/H statements into the #ollowing4
PC+PmodulenamePn E=*E? +22 address
Where
modulename is the name o# the source #ile.
n is a se:uential number.
address is the address speci#ied in the C/H statement.
See Also 2SEG& C0DE& DSEG& ISEG& 6SEG
E)am!le CE= 000J# absolute code segement at address 0'J
n The DSEG statement selects an absolute segment within *ATA space.
"# the optional address is included& the assembler starts the absolute segment #rom thataddress. The $alid address range is 00h!0h (data memory resides #rom 00h!Gh ands reside #rom 80h!0h).
"# the optional address is omitted& the assembler starts the absolute segment #romaddress 0 (i# no prior absolute *ATA segment was de#ined). "# an absolute *ATAsegment was pre$iously de#ined& the assembler continues #rom the end o# thatsegment.
Note
The start address must be an absolute expression.
The AE5 Assembler con$erts */H statements into the #ollowing4
PPmodulenamePn E=*E? +22 address
Where
modulename is the name o# the source #ile.
n is a se:uential number.
address is the address speci#ied in the */H statement.
E)am!le E= 0'T0 absolute segment at T03
*6 H absolute data 9ord !ariable 9it# name
*6
E*6D T absolute data d9ord (JH-bit) !ariable 9it# name
The ISEG statement selects an absolute segment within "*ATA space.
"# the optional address is included& the assembler starts the absolute segment #romthat address. The $alid address range is 00h!0h.
"# the optional address is omitted& the assembler starts the absolute segment #romaddress 0 (i# no prior absolute "*ATA segment was de#ined). "# an absolute "*ATAsegment was pre$iously de#ined& the assembler continues #rom the end o# thatsegment.
Note
The start address must be an absolute expression.
The AE5 Assembler con$erts "/H statements into the #ollowing4
P4PmodulenamePn E=*E? +22 address
Where
modulename is the name o# the source #ile.
n is a se:uential number.
address is the address speci#ied in the "/H statement.
The C0DE and C0NST memory classes are typically stored in ' that may be either o##!chip or on!chip. The C0DE memory class is used #or the actual program code while the
C0NST memory class is used #or constant $ariables declared in co#e space.
"n addition& up to =B code ban-s may be used #or code ban-ing applications. hile these are
technically located in code space& they are assigned their own address space.
6DATA an# PDATA
The 6DATA memory class is typically stored in A' that may be o##!chip or on!chip (on
newer de$ices). "t contains external program data (named because it was o##!chip on theoriginal 805 de$ices) including $ariables declared with the )#ata and !#ata memory
types.
The PDATA memory class is a B5F!byte page within the 6DATAmemory class.
e$eral new $ariants o# the 805 extend the code andQor xdata space o# the classic 805
with address extension registers.
The #ollowing table shows the memory classes used #or programming the extended 805de$ices. These memory classes are a$ailable #or classic 805 de$ices when you are using
memory ban-ing with the 2E5 lin-erQlocater. "n addition to the code ban-ing -nown #romthe ,25 lin-erQlocater& the 2E5 lin-erQlocator supports also data ban-ing #or xdata and
code areas with standard 805 de$ices.
MemoryClass A##ress 1an"e Descri!tion
*ATA *400 K *4G *irect addressable on chip A'.
,"T *4B0 K *4B bit addressable A'; accessed bit instructions.
"*ATA "400 K "4 "ndirect addressable on chip A'; can be
accessed with R0 or R.E*ATA E40000 K E4 FN M, A' (readQwrite access). Accessed with
'E instruction.
6*ATA E40000 K E4 F ', A' (readQwrite access). Accessed with
'E instruction and extended *3T.
C*/ C40000 K C4 FN M, ' (only read access possible). 9sed #orexecutable code or constants.
/C*/ C40000 K C4 F ', ' (only read access possible). 9sed #orconstants. "n some modes o# the *allas =?0
architecture also program execution is possible. .
,A<M 0
J ,A<M =
,040000 K ,04
,=40000 K,=4
Code ,an-s #or expanding the program code space
to =B x FNM, '.
Note
The memory pre#ixes *4 "4 E4 C4 ,04 .. ,=4 cannot be used at Ax5 assembler
le$el. The memory pre#ix is only listed #or better understanding. The 2x5 lin-erQlocaterand se$eral *ebugging tools& #or example the SisionB *ebugger& are using memory
pre#ixes to identi#y the memory class o# the address.
"# you are using the *allas =?0 contiguous mode the address space #or C*/ can be
The C0DE and EC0DE memory classes are typically stored in ' that may be either o##!chip or on!chip. The C0DE memory class may be used #or program code and re#ers to the
#irst FNM (or ,an- 0) o# this read!only memory area.
The EC0DE memory class is used #or constant $ariables declared in co#e space abo$e the
"n se$eral $ariants the *3T register is expanded to a BN!bit register with an DP6 . orexample& the *allasQ'axim =?0 pro$ides new operating modes where this addressing is
enabled. +ou may e$en use the 6C<T and 6*ATA memory classes with classic 805de$ices by using the memory ban-ing a$ailable in 2E5.
2an; 3 through 2an; K allow your program to expand up to N 'bytes when using
memory ban-ing.
6DATA an# BDATA
The 6DATA memory class re#ers to the #irst FNM o# A' which may be o##!chip or on!chip.
The BDATA memory class is used when A' memory re:uirements exceed FNM bytes. Thismemory class allows you to de#ine up to F 'bytes
The A5 assembler de#ines the #ollowing additional reser$ed symbols which are special
#unction registers () o# the classic 805 'C9. These de#initions may be disabledusing the N0M0D,- control statement. The prede#ined symbols are reser$ed symbols
and may not be rede#ined in your program.
AC
ACC$
,
C+
*36
*32
/A /
/T0
/T
/E0
/E
0
"/
"/0
"/
"<T0
"<T
"T0
"T
3
30 3
3B
3=
3
3
3T0
3T
3E0
3E
,8
*
/<
"
0
E* ,9
C<
'0
'
'B
3
T
T,8
TC<
T0
T
T60
T6
T"
T20
T2 T'*
T
T0
T
TE*
The AE5 assembler de#ines the #ollowing additional reser$ed symbols which comprise the
additional instructions and registers o# the 3hilips 80C5'E architecture.
