110 |
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Chapter 4. Assembler Directives |
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HCSEG |
SEGMENT |
HCONST SEG |
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Defines a segment with the name HCSEG with the memory class HCONST. The segment is SEGMENT aligned, this means it starts on a 64KByte segment.
RSEG
The RSEG directive selects a generic segment that was previously declared using the SEGMENT directive. The RSEG directive uses the following format:
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RSEG segment |
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where |
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segment |
is the name of a segment that was previously defined using |
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the SEGMENT directive. Once selected, the specified |
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segment remains active until a new segment is specified. |
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Example |
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MYPROG |
SEGMENT |
CODE |
; declare a segment |
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RSEG |
MYPROG |
; select the segment |
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MOV |
A, #0 |
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MOV |
P0, A |
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Shaded directives and options are available only in AX51 and A251.
Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
111 |
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BSEG, CSEG, DSEG, ISEG, XSEG
The BSEG, CSEG, DSEG, ISEG, XSEG directives select an absolute segment. This directives use the following formats:
BSEG |
AT |
address |
defines an absolute BIT segment. |
CSEG |
AT |
address |
defines an absolute CODE segment. |
DSEG |
AT |
address |
defines an absolute DATA segment. |
ISEG |
AT |
address |
defines an absolute IDATA segment. |
XSEG |
AT |
address |
defines an absolute XDATA segment. |
where |
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address |
is an optional absolute base address at which the segment |
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begins. The address may not contain any forward |
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references and must be an expression that can be evaluated |
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to a valid address. |
CSEG, DSEG, ISEG, BSEG and XSEG select an absolute segment within the |
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code, internal data, indirect internal data, bit, or external data address spaces. If |
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you choose to specify an absolute address (by including AT address), the |
assembler terminates the last absolute segment, if any, of the specified segment type, and creates a new absolute segment starting at that address. If you do not specify an address, the last absolute segment of the specified type is continued. If no absolute segment of this type was selected and the absolute address is omitted, a new segment is created starting at location 0. You cannot use any forward references and the start address must be an absolute expression.
The AX51 and A251 Macro Assembler supports the BSEG, CSEG, DSEG, ISEG, and XSEG directives for A51 compatibility.
Shaded directives and options are available only in AX51 and A251.
112 |
Chapter 4. Assembler Directives |
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These directives are converted to standard segments as follows:
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A51 Directive |
Converted to AX51/A251 Segment Declaration |
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BSEG AT 20H.1 |
?BI?modulename?n SEGMENT OFFS 20H.1 |
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CSEG AT 1234H |
?CO?modulename?n SEGMENT OFFS 1234H |
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DSEG AT 40H |
?DT?modulename?n SEGMENT OFFS 40H |
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ISEG AT 80H |
?ID?modulename?n SEGMENT OFFS 80H |
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XSEG AT 5100H |
?XD?modulename?n SEGMENT OFFS 5100H |
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where |
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modulname |
is the name of the current assembler module |
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n |
is a sequential number incremented for every absolute |
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segment. |
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Examples |
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BSEG AT 30h |
; absolute bit segment @ 30h |
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DEC_FLAG: |
DBIT |
1 |
; absolute bit |
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INC_FLAG: |
DBIT |
1 |
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CSEG AT 100h |
; absolute code segment @ 100h |
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PARITY_TAB: |
DB |
00h |
; parity for 00h |
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DB |
01h |
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01h |
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DB |
01h |
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02h |
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DB |
00h |
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03h |
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DB |
01h |
; |
FEh |
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DB |
00h |
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FFh |
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DSEG AT 40h |
; absolute data segment @ 40h |
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TMP_A: |
DS |
2 |
; absolute data word |
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TMP_B: |
DS |
4 |
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ISEG AT 40h |
; abs indirect data seg @ 40h |
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TMP_IA: |
DS |
2 |
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TMP_IB: |
DS |
4 |
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XSEG AT 1000h |
; abs external data seg @ 1000h |
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OEMNAME: |
DS |
25 |
; abs external data |
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PRDNAME: |
DS |
25 |
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VERSION: |
DS |
25 |
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Shaded directives and options are available only in AX51 and A251.