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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- Pseudo Instructions --><HTML><HEAD><TITLE>Pseudo Instructions</TITLE></HEAD><BODY BACKGROUND="spiral.gif" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#990099" ALINK="#FF0000"><TABLE WIDTH="98%"><TR><TD WIDTH=60 VALIGN=BOTTOM NOWRAP><IMG SRC="transp.gif" ALT="" WIDTH=60 HEIGHT=20></TD><TD><!-- Ab hier Seitentext: --><BIG><BR><P><STRONG><U>III.6 Pseudo Instructions</U></STRONG></P><P>In the subsequent paragraphs, all <NOBR>ASEM-51</NOBR> pseudo instructions aredescribed. Lexical symbols are written in lower case letters, while assemblerkeywords are written in upper case.<BR>Instruction arguments are represented by <arg>, <arg1> or something likethat. Numeric expressions are represented by <expr>, <expr1> and so on.Syntax elements enclosed in brackets are optional.<BR>The ellipsis "..." means always "a list with any number of elements".</P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>DB <arg1> [,<arg2> [,<arg3> ... ]]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define bytes</BIG></TH></TR></TABLE><BLOCKQUOTE>The DB instruction reserves and initializes a number of bytes withthe values defined by the arguments. The arguments may either beexpressions (which must evaluate to 8-bit values) or characterstrings of any length. DB is only allowed in the CODE segment!<BR><BR>Example: <CODE>DB 19,'January',98,(3*7+12)/11</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>DW <expr1> [,<expr2> [,<expr3> ... ]]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define words</BIG></TH></TR></TABLE><BLOCKQUOTE>The DW instruction reserves and initializes a number of words withthe values defined by the arguments. Every argument may be anarbitrary expression and requires two bytes of space.DW is only allowed in the CODE segment!<BR><BR>Example: <CODE>DW 0,0C800H,1999,4711</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>DS <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define space</BIG></TH></TR></TABLE><BLOCKQUOTE>Reserves a number of uninitialized bytes in the current segment.The value of <expr> must be known on <NOBR>pass 1</NOBR>!DS is allowed in every segment, except in the BIT segment!<BR><BR>Example: <CODE>DS 200H</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>DBIT <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define bits</BIG></TH></TR></TABLE><BLOCKQUOTE>Reserves a number of uninitialized bits.The value of <expr> must be known on <NOBR>pass 1</NOBR>!DBIT is only allowed in the BIT segment!<BR><BR>Example: <CODE>DBIT 16</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>NAME <symbol></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define module name</BIG></TH></TR></TABLE><BLOCKQUOTE>Defines a module name for the <NOBR>OMF-51</NOBR> object file.If no module name is defined, the module name is derived from thesource file name.When generating <NOBR>Intel-HEX</NOBR> file output, the NAME instructionhas no effect. The module name must be a legal assembler symbol.Only one NAME instruction is allowed within the program. The symbolhowever, may be redefined in the subsequent program.<BR><BR>Example: <CODE>NAME My_1st_Program</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>ORG <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>origin of segment location</BIG></TH></TR></TABLE><BLOCKQUOTE>Sets the location counter of the current segment to the value <expr>.The value of <expr> must be known on <NOBR>pass 1</NOBR>!It must be greater or equal to the segment base address.The default value of all location counters at program start is 0.<BR><BR>Example: <CODE>ORG 08000H</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>USING <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>using register bank</BIG></TH></TR></TABLE><BLOCKQUOTE>Sets the register bank used to <expr>, which must be in the rangeof 0...3. The USING instruction only affects the values of thespecial assembler symbols AR0, ... , AR7 representing the directaddresses of registers R0, ... , R7 in the current register bank.The value of <expr> must be known on <NOBR>pass 1</NOBR>!The default value for the register bank is 0.<BR><BR>Example: <CODE>USING 1</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>END</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>end of program</BIG></TH></TR></TABLE><BLOCKQUOTE>This must be the last statement in the source file. After the ENDstatement only commentary and blank lines are allowed!<BR><BR>Example: <CODE>END ;end of program</CODE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> EQU <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define numeric constant</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> EQU <reg></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define invariant register</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> SET <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define numeric variable</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> SET <reg></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define variable register</BIG></TH></TR></TABLE><BLOCKQUOTE>The EQU instruction defines a symbol for a numeric constant or aregister. If a numeric expression <expr> is assigned to the symbol,it will be of the type NUMBER. If a register <reg> is assigned tothe symbol, it will be of the type REGISTER. <reg> may be one of thespecial assembler symbols A, R0, R1, R2, R3, R3, R4, R5, R6, or R7.<BR>A symbol once defined with EQU can never be changed!<BR>The SET instruction is working quite similar to EQU. However, symbolsdefined with SET can be redefined with subsequent SET instructions!The values of <expr> and <reg> must be known on <NOBR>pass 1</NOBR>!<BR>A symbol that has been SET, cannot be redefined with EQU!<BR>A symbol that has been EQU'd cannot be reSET!<BR>On <NOBR>pass 2</NOBR>, forward references to a SET symbol always evaluateto the last value, the symbol has been SET to on <NOBR>pass 1</NOBR>.<BR>Register symbols can be used as instruction operands within thewhole program instead of the corresponding registers.<BR>Forward references to register symbols are not allowed!<BR><BR>Examples:<PRE> MAXMONTH EQU 12 OCTOBER EQU MAXMONTH-2 COUNTREG EQU R5 CHAPTER SET 1 CHAPTER SET CHAPTER+1 CHAPTER SET A</PRE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> CODE <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define ROM address</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> DATA <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define direct RAM address</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> IDATA <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define indirect RAM address</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> BIT <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define bit address</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE><symbol> XDATA <expr></CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>define external RAM address</BIG></TH></TR></TABLE><BLOCKQUOTE>These instructions define symbolic addresses for the five 8051memory segments (address spaces). For DATA, IDATA and BIT typesymbols, the value of <expr> must not exceed 0FFH!The value of <expr> must be known on <NOBR>pass 1</NOBR>!<BR>Once defined with one of the above instructions, the symbols cannotbe redefined.<BR><BR>Examples:<PRE> EPROM CODE 08000H STACK DATA 7 V24BUF IDATA 080H REDLED BIT P1.5 SAMPLER XDATA 0100H</PRE></BLOCKQUOTE></P><BR><P><TABLE WIDTH="85%"><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>CSEG [AT <expr>]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>switch to CODE segment [at address]</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>DSEG [AT <expr>]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>switch to DATA segment [at address]</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>ISEG [AT <expr>]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>switch to IDATA segment [at address]</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>BSEG [AT <expr>]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>switch to BIT segment [at address]</BIG></TH></TR><TR><TH ALIGN=LEFT NOWRAP><BIG><STRONG><CODE>XSEG [AT <expr>]</CODE></STRONG></BIG></TH><TH ALIGN=RIGHT NOWRAP><BIG>switch to XDATA segment [at address]</BIG></TH></TR></TABLE><BLOCKQUOTE>These instructions switch to one of the five 8051 address spaces.If a segment base address is specified with "AT <expr>", a newabsolute segment is started, and the location counter is set to<expr>. If "AT <expr>" is omitted, the location counter keeps theprevious value of the particular segment.<BR>The value of <expr> must be known on <NOBR>pass 1</NOBR>!<BR>At program start, the default segment is CODE and the base addressesand location counters of all segments are set to zero.<BR><BR>Examples:</BLOCKQUOTE><PRE> DSEG ;switch to previous DATA segment CSEG AT 8000h ;start a new CODE segment at address 8000H XSEG at 0 ;start a new XDATA segment at address 0</PRE></P></BIG><!-- Seitentext Ende --><P><BR><BR><CENTER><TABLE WIDTH="70%"><TR><TH><A HREF="contents.htm"><IMG SRC="home.gif" ALT="[contents]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="language.htm"><IMG SRC="up.gif" ALT="[up]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="instrset.htm"><IMG SRC="back.gif" ALT="[back]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH> <TH><A HREF="segment.htm"><IMG SRC="next.gif" ALT="[next]" BORDER=0 WIDTH=32 HEIGHT=32></A></TH></TR></TABLE></CENTER></P></TD></TR></TABLE></BODY></HTML>⌨️ 快捷键说明
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