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High-Level Language Controls
The Lx51 linker/locator provides controls that have to do with the high-level |
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languages Cx51 and PL/M-51 and the real-time operating systems RTXx51. |
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For example, you can control whether or not the Lx51 linker/locator includes |
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automatically the run-time library and whether or overlays the local variable |
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areas of C and PL/M-51 functions. |
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The following table provides an overview of these controls. For a detailed |
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description of each control refer to the page specified in the table. |
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BL51 |
LX51, L251 |
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Description |
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NODEFAULT |
NODEFAULT |
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Excludes modules from the run-time |
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LIBRARY |
LIBRARY |
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libraries. |
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NOOVERLAY |
NOOVERLAY |
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Prevents overlaying or overlapping local bit |
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and data segments. |
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OVERLAY |
OVERLAY |
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Lets you change call references between |
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functions and segments for data overlaying |
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program flow analysis. |
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RECURSIONS |
RECURSIONS |
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Allows you to analyze the call tree of |
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complex recursive applications. |
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REGFILE |
REGFILE |
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Specifies the name of the generated file to |
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contain register usage information. |
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– |
RTX251 |
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Includes support for the RTX-251 full |
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real-time kernel. |
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RTX51 |
RTX51 |
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Includes support for the RTX-51 full |
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real-time kernel. |
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RTX51TINY |
RTX51TINY |
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Includes support for the RTX-51 tiny |
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real-time kernel. |
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SPEEDOVL |
– |
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Ignore during the overlay analysis |
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references from constant segments to |
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program code. |
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Chapter 9. Linker/Locator |
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NODEFAULTLIBRARY |
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Abbreviation: |
NLIB |
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Arguments: |
None |
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Default: |
The run-time libraries of Cx51, RTXx51, and PL/M-51 are |
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searched to resolve external references in your C or PL/M |
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programs. |
The path of the run-time libraries can be set for BL51 and LX51 with the C51LIB environment variable and for L251 with the C251LIB environment variable. This variable is the defined with the SET command that is typically entered in the AUTOEXEC.BAT batch file as shown below:
SET C51LIB=C:\KEIL\C51\LIB
In µVision2 the path for run-time libraries can be specified in the dialog Project – File Extensions, Books and Environment under environment setup – LIB folder.
If no environment variable is set, the linker tries to locate the libraries in: path_of_the_EXE_file\..\LIB\. In a typical installation of the tool chain this sets the correct path for the run-time libraries to \C51\LIB\ or \C251\LIB. These folders contain the run-time libraries for the Cx51 compiler and the RTXx51 real-time operating system.
The libraries that are automatically searched depend on the memory model and floating-point requirements of your application. For more information refer to the Cx51 Compiler User’s Guide.
µVision2 Control: Options – Lx51 Misc – Misc Controls: enter the control.
Description: Use the NODEFAULTLIBRARY control to prevent the
Lx51 linker/locator from automatically including run-time libraries.
Example: |
BL51 MYPROG.OBJ NODEFAULTLIBRARY |
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Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
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NOOVERLAY
Abbreviation: |
NOOL |
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Arguments: |
None |
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Default: |
The Lx51 linker/locater is analyzing your program and |
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overlays the segments of local variables and function |
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arguments. |
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µVision2 Control: Options – Lx51 Misc – Misc Controls: enter the control.
Description: The NOOVERLAY control disables the overlay analysis and the data overlaying. When this control is specified, the Lx51 linker/locator does not overlay the data space of local variables and function arguments.
Examples: |
LX51 MYPROG.OBJ NOOVERLAY |
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Chapter 9. Linker/Locator |
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OVERLAY |
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Abbreviation: |
OL |
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Arguments: |
OVERLAY (sfname { ! | ~ } sfname , … ) |
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OVERLAY (sfname { ! | ~ } (sfname, sfname , … ) , … ) |
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OVERLAY (sfname ! *) |
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OVERLAY (* ! sfname) |
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Default: |
The Lx51 linker/locater is analyses the call tree of your |
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program and assumes normal program flow without indirect |
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calls via function pointers. |
µVision2 Control: Options – Lx51 Misc – Overlay.
Description: The OVERLAY control allows you to modify the call tree as it is recognized by the Lx51 linker/locater in the overlay analysis. Adjustments to the program call tree are typically required when your application uses function pointers or contains virtual program jumps as it is the case in the scheduler of a real-time operating system. The different forms of the overlay control are shown below:
Control Specification |
Description |
OVERLAY (* ! sfname) |
Add new root for sfname. |
OVERLAY (sfname ! *) |
Exclude sfname from the |
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overlay analysis and locate |
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data & bit segments in non- |
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overlaid memory. This |
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does not influence data |
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overlaying of other |
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functions. |
OVERLAY (sfname ! sfname1) |
Add virtual call references |
OVERLAY (sfname ! (sfname1, sfname2)) |
to segments or functions. |
OVERLAY (sfname ~ sfname1) |
Ignore call references |
OVERLAY (sfname ~ (sfname1, sfname2)) |
between segments or |
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functions. |
sfname can be the name of a function or a segment.
Refer to “Using the Overlay Control” on page 282 for program examples that require the OVERLAY control.
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Chapter 9. Linker/Locator |
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RECURSIONS |
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Abbreviation: |
RC |
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Arguments: |
RECURSIONS (number of recursions) |
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Default: |
RECURSIONS (10) |
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µVision2 Control: |
Options – Lx51 Misc – Misc Controls: enter the control. |
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Description: |
The RECURSIONS control allows you to specify the |
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number of recursions that are allowed before the Lx51 |
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linker/locator responds with: |
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FATAL ERROR 232: APPLICATION CONTAINS TOO MANY RECURSIONS. |
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Each time the linker encounters a recursive call during the |
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overlay analysis of the application, this recursive call is |
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automatically removed from the call tree and the overlay |
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analysis is restarted. You might increase the number of |
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accepted recursions on very complex recursive applications. |
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However this might increase significantly the execution time |
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of the Lx51 linker/locater. |
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If your application contains many pointer to function tables, |
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you might receive the FATAL ERROR 232 before you have |
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corrected the call tree with the OVERLAY control. The |
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RECURSIONS control allows you in such situations to |
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analysis the OVERLAY MAP of your application. Refer to |
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“Pointer to a Function in Arrays or Tables” on page 286 for |
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more information on correcting the call tree. |
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See Also: |
OVERLAY, SPEEDOVL |
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Example: |
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LX51 MYPROG.OBJ,A.OBJ,B.OBJ RECURSIONS (100) |
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Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
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REGFILE
Abbreviation: |
RF |
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Arguments: |
REGFILE (filename) |
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Default: |
No register usage file is generated. |
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µVision2 Control: |
Options – Cx51 Compiler – Global Register Coloring. |
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Description: |
The REGFILE control allows you to specify the name of |
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the register usage file generated by the Lx51 linker/locator. |
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The information in this file is used for global register |
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optimization by the Cx51 compiler. The register usage |
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information allows the Cx51 compiler to optimize the use of |
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registers when calling external functions. |
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Example: |
In this example, the LX51 linker/locator generates the file |
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MYPROG.REG that contains register usage information. |
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LX51 MYPROG.OBJ,A.OBJ,B.OBJ REGFILE(MYPROG.REG)
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RTX251, RTX51, RTX51TINY |
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Abbreviation: |
None |
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Arguments: |
None |
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Default: |
None |
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µVision2 Control: |
Options – Target – Operating System. |
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Description: |
These controls specify to the Lx51 linker/locator that the |
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application should be linked for use with the RTXx51 real- |
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time multitasking operating system. This involves resolving |
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references within your program to RTXx51 functions found |
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in the library of the real-time operating system. |
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The control that you should use, depends on the real-time |
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operating system that you are using in your application: |
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Control |
Real-Time Operating System used |
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RTX251 |
RTX251 Full Multitasking RTOS. |
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RTX51 |
RTX51 Full Multitasking RTOS. |
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RTX51TINY |
RTX51 Tiny Multitasking RTOS. |
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Examples: |
Linker/Locater invocation for RTX51 Full: |
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BL51 RTX_EX1.OBJ RTX51 |
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Linker/Locater invocation for RTX251 Full: |
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L251 RTX_EX1.OBJ RTX251 |
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Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
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SPEEDOVL
Restriction: |
This control is available in BL51 only. LX51 and L251 |
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always ignore references from constant segments to program |
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code during the overlay analysis. |
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Abbreviation: |
SP |
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Arguments: |
None |
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Default: |
BL51 does not ignore the references from constant segments |
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to program code during the overlay analysis. |
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µVision2 Control: Options – BL51 Misc – Misc Controls: enter the control. |
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Description: |
The RECURSIONS control instructs BL51 to ignore |
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references from constant segments to program code during |
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the overlay analysis. This improves the execution speed of |
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the BL51 linker/locater during overlay analysis and is useful |
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for applications that are using “Pointer to a Function in |
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Arrays or Tables” as described on page 286. However, the |
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usage of the SPEEDOVL control makes the linker |
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incompatible to existing applications that are using the |
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OVERLAY control to correct the call tree of the |
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application. |
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See Also: |
OVERLAY, SPEEDOVL |
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Example: |
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BL51 MYPROG.OBJ SPEEDOVL |
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