Intel iAPX 86 User Manual page 257

Additional Information for Intellec Series IV Users
iAPX 86,88 Family Utilities
K-12
MODULE INFORMATION:
END
CODE AREA SIZE
CONSTANT AREA SIZE
VARIABLE AREA SIZE
MAXIMUM STACK SIZE
918 LINES READ
o
PROGRAM ERROR(S)
OF PL/M-86 COMPILATION
MODULE INFORMATION
CODE AREA SIZE
CONSTANT AREA SIZE
VARIABLE AREA SIZE
MAXIMUM STACK SIZE
918 LINES READ
o
PROGRAM ERROR(S)
END OF PL/M-86 COMPILATION
o
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0040H
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t
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t his
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t
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the CODE segment
the CONST segment
the D A T A s e gme n t
the STACK segment
OV2's segment size information
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t his
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t his
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t his
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t his
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the CODE segment
the CONST segment
the DATA segment
the STACK segment
Figure K-7. Module Information for Overlays
Note that the length of the root's code segment and the
l~lfger
overlay's (OV 1 's) code
segment must fit within 64K. This means that the code for the overlays must be in a
part of memory contiguous with the root (to avoid altering the CS register during
execution). OV2's CONST and DATA segments are larger than OV
1
's so that the
STACK segment must be placed to leave room for OV2's CONST and DATA
segments. If the overlays share the STACK and MEMORY segments with the root,
they must be located at the same address.
After computing the required location for the root's DGROUP and STACK, we can
locate the root module. The resulting file will not be executable, but it allows us to
resolve references to the root's code and data symbols in the overlays. The following
LOC86 invocation will leave room for the overlays' code segments and place the
DGROUP in the first unused memory location. (In the command line below, the DS
register is initialized to OFFCH, and the CS register is initialized to 0.) The STACK
and MEMORY segments will be located abov1e OV2's DATA segment:
>
»
»
»
»
Once the root is located, we can use it to resolve external references in the overlay
modules. The overlay modules cannot call each other, since only one is resident in
memory at any time. The link commands are shown below. The NOPUBLICS with
the EXCEPT control is used to avoid conflicts when we use the located overlays to
resolve external references in the root:
>
»
>
»
LINK86 OV1.0BJ,PUBLICSONLY(RO
NOPUBLICS EXCEPT(OV1CODE, OV1
LINK860V2.0BJ,PUBLICSONLY(RO
NOPUBLICS EXCEPT (OV2CODE, OV
The PUBLICSONL Y control resolves references to public symbols contained in the
root.