Segment and Memory Location Controls

The Lx51 linker/locator locates segments in according their memory class and follows a predefined order of precedence. The standard allocation algorithm usually produces the best workable solution and does not requiring you to enter any segment names on the command line. The controls described in this section allow you to define the physical memory layout of your target system and more closely control the location of segments within the different memory classes. Refer to “Locating Programs to Physical Memory” on page 273 for examples on how to define the available memory in your x51 system.

BANKx

µVision2 Control: Options – BL51 Misc – Misc Controls – enter the control.

Description: Use the BANKx control to specify a code bank for segments (x in BANKx is replaced by a bank number). Refer to “Bank Switching” on page 293 for more information about the code banking controls.

µVision2 Control: Options – BL51 Locate – Bit.

Description: The BIT control allows you to specify:

The starting address for segments placed in the bit-addressable internal data space

The order of segments within the bit-addressable internal data space

The absolute memory location of segments in the bit-addressable internal data space.

Addresses that you specify with the BIT control are bit addresses. Bit addresses 00h through 7Fh reference bits in DATA memory bytes from byte address 20h to 2Fh (16 bytes of 8 bits each, 16 × 8 = 128 = 80h). Bit addresses that are evenly divisible by 8 are aligned on a byte boundary. A DATA segment that is bit-addressable can be located with the BIT control; however, the bit address specified must be byte aligned, that means evenly divisible by 8.

To specify the order for segments, you must include the segment names, separated by commas. The following

example places the ?DT?A, ?DT?B, and ?DT?C segments at 9 the beginning of the bit-addressable DATA memory.

BL51 MYPROG.OBJ,A.OBJ,B.OBJ,C.OBJ BIT(?DT?A,?DT?B,?DT?C)

You may also specify the bit address for the segments. The following example places the ?DT?A and ?DT?B segments at 28h and 30h:

BL51 MYPROG.OBJ,A.OBJ,B.OBJ BIT(?DT?A(28h),?DT?B(30h))

µVision2 Control: Options – Lx51 Locate – User Classes.

Description: The CLASSES control specifies the physical address range for segments within a memory class. The CLASSES control provides an efficient way to define the physical memory layout. If the address limits for a memory class are not specified with the CLASSES control, the Lx51 linker/locater uses the physical address limits of the memory class. The address ranges that are used are listed in the linker MAP file in the section ACTIVE MEMORY CLASSES. It is recommended to check this section of the MAP file, since it lists where the Lx51 linker/locater assumes memory in your target hardware. More information about “Locating Programs to Physical Memory” can be found on page 273.

With the CLASSES control the absolute address for segments with the relocation type OFFS can be modified. For more information on how to declare such segments refer to “Relocation Type” on page 108. The offset is specified as first address in the range field with a ‘$’ prefix, for example:

CLASSES (CODE ($0xFF8000, 0xFF8000 - 0xFFFFFF). In this case all segments that are defined with the OFFS relocation type, are redirected to the address 0xFF8000. Typically the interrupt and reset vectors of a program are defined this way. In this way, you can quickly redirect these vectors, for example, when you are debugging programs with the Monitor-251 installed at address 0xFF0000.

L251 MYFILE.OBJ &

CLASSES (EDATA (0 - 0x41F, 0x2000H - 0x3FFF),

CODE (0xFF0000 - 0xFF7FFF))

This example defines the memory classes for a classic 8051 device:

LX51 MYFILE.OBJ

CLASSES (IDATA (I:0-I:0xFF), XDATA (X:0-X:0xEFFF),

CODE (C:0-C:0x7FFF, C:0xC000-C:0xFFFF))

In this example the user-defined memory class

XDATA_FLASH is defined. Refer to “User-defined Class

Names” on page 107 for more information.

LX51 MYFILE.OBJ

CLASSES (XDATA_FLASH (X:0x8000-X:0xEFFF))

µVision2 Control: Options – BL51 Locate – Code Range, Code.

Description: The CODE control allows you to specify:

BL51 MYPROG.OBJ CODE(0 - 0x3FFF, 0x8000 - 0xFFFF)

To specify the order for segments, you must include the names of the segments separated by commas. The following example will place the ?PR?FUNC1?A and ?PR?FUNC2?A segments at the beginning of the CODE memory:

BL51 A.OBJ CODE(?PR?FUNC1?A, ?PR?FUNC2?A)

You can also specify the memory location for a segment. The example below will place the ?PR?FUNC1?A segment at 800h and the ?PR?FUNC2?A segment after at this segment:

BL51 A.OBJ CODE(?PR?FUNC1?A (0x800), ?PR?FUNC2?A)

DATA

µVision2 Control: Options – BL51 Locate – Data.

Description: The DATA control allows you to specify:

segments be located at or after address 48 decimal (30 hex) in the on-chip DATA memory:

BL51 MYPROG.OBJ DATA(48)

or

BL51 MYPROG.OBJ DATA(0x30)

To specify the order for segments, you must include the names of the segments separated by commas. The following example will place the ?DT?A, ?DT?B, and ?DT?C segments at the beginning of the DATA memory:

BL51 A.OBJ,B.OBJ,C.OBJ DATA(?DT?A,?DT?B,?DT?C)

You can also specify the memory location. The example below will place the ?DT?A and ?DT?B segments at 28h and 30h in the DATA memory:

BL51 MYPROG.OBJ,A.OBJ,B.OBJ DATA(?DT?A(28h),?DT?B(30h))

µVision2 Control: Options – BL51 Locate – Idata.

Description: The IDATA control allows you to specify:

segments be located at or after address 64 decimal (40 hex) in the IDATA memory.

BL51 MYPROG.OBJ IDATA(64)

or

BL51 MYPROG.OBJ IDATA(0x40)

To specify the order for segments, you must include the names of the segments separated by commas. The following example places the ?ID?A, ?ID?B, and ?ID?C segments at the beginning of the IDATA memory:

BL51 A.OBJ,B.OBJ,C.OBJ IDATA(?ID?A,?ID?B,?ID?C)

You may also specify the memory location. This example places the ?ID?A and ?ID?B segments at 30h and 40h in the on-chip IDATA memory:

BL51 MYPROG.OBJ,A.OBJ,B.OBJ IDATA(?ID?A(30h),?ID?B(40h))

NOSORTSIZE

µVision2 Control: Options – Lx51 Misc – Misc Controls: enter the control.

Description: The NOSORTSIZE control allows you disable the sorting algorithm. In this case the linker allocates the memory in the order the segments appear in the input files.

BL51 MYPROG.OBJ PDATA(0x8000)

PRECEDE

µVision2 Control: Options – BL51 Locate – Precede.

Description: The PRECEDE control allows you to specify segments that lie in the on-chip DATA memory that should precede other segments in that memory space. Segments that you specify with this control are located after the BL51 linker/locator has located register banks and any absolute BIT, DATA, and IDATA segments, but before any other segments in the internal DATA memory.

RESERVE

Default: no memory areas are reserved.

µVision2 Control: Options – Lx51 Misc – Reserve.

Description: The RESERVE directive allows you to prevent Lx51 from locating segments in the specified address ranges of the physical memory. The Lx51 linker/locater will not use all memory address within the specified address range.

µVision2 Control: Options – Lx51 Locate – User Segments.

Description: The SEGMENTS control allows you to specify:

The absolute memory location of a segment. The absolute address can be either a start or an end address.

The order of segments within the memory. Segments may be located as first or last segment. Segments defined in the SEGMENTS control are allocated sequentially. By default, the first segment is located at the lowest possible address range (specified with the CLASSES control). Subsequent segments are located at ascending addresses. When you are using the keyword LAST in the address field, then the segment is located as last segment for this memory class.

A segment can be executed in RAM whereas the content is stored in the ROM memory class. Such segments need to be copied from ROM to RAM before execution. You can specify both the ROM address that stores the content and the RAM address that is used to address the segment during program execution. This syntax is:

SEGMENTS Syntax for Store in ROM and Executed in RAM

SEGMENTS (segment_name(exec_address)[store_address], …)

exec_address specifies the execution address for the segment. store_address is the address where the segment is stored in ROM.

SEGMENTS (segment_name(exec_address)[], …)

If you specify empty brackets [] for the store_address the segment will be stored within the address range of the SROM memory class.

SEGMENTS (segment_name(exec_address)[!store_address], …)

Lx51 does not reserve the space for execution, if the exclamation mark is given before the store_address. This is useful, if the segment content is copied over RAM that is temporarily used, for example the stack area.

SEGMENTS (segment_name(exec_address)[!], …)

If not store_address is given the segment is stored within the range of the SROM memory class. Also here not space is reserved for execution.

LX51 A.OBJ,B.OBJ SEGMENTS (?DT?A(D:0x28),?DT?B(D:0x30))

To specify the order for segments, you must include the names of the segment separated by commas. The following example places the ?DT?A, ?DT?B, and ?DT?C segments at the beginning of the memory class. If these segments belong to the DATA memory class they will be places as first segments in the DATA memory class.

L251 A.OBJ,B.OBJ,C.OBJ SEGMENTS(?DT?A,?DT?B,?DT?C)

A segment can be located to a code bank. The next example locates the segment ?PR?FUNC2?B into code bank 0 and the segment ?PR?FUNC1?A to address 0x8000 in code bank 1.

L251 BANK0 {A.OBJ}, BANK1 {B.OBJ}

SEGMENTS(?PR?FUNC2?B (B0:), ?PR?FUNC1?A (B1:0x8000))

You can also specify that a segment should be placed as last segment in a memory class by using the LAST keyword as address specification. The following example places the segment ?DT?A as last segment in the DATA memory class:

LX51 A.OBJ,B.OBJ,C.OBJ SEGMENTS(?DT?B(LAST))

The prefix '^' before the address specifies the end address for a segment. The following command places the segment ?PR?SUM?B in memory so that it ends at address 0xFF8000.

L251 A.OBJ,B.OBJ SEGMENTS (?PR?SUM?B(^0xFF8000))

Next, the segment ?PR?FUNC1?A is assigned an execution address of 0x4000 and a storage address of 0xFF8000.

L251 A.OBJ SEGMENTS (?PR?FUNC1?A(0x4000)[0xFF8000])

The last example uses only an exclamation point as store_ address. This means that no memory is reserved at address 0x2000 and the section will be stored within the address range of the SROM memory class.

L251 A.OBJ SEGMENTS (?PR?FUNC1?A(0x2000)[!])

µVision2 Control: Options – Lx51 Misc – Misc Controls: enter the control.

STACK

µVision2 Control: Options – BL51 Locate – Stack.

Description: The STACK control locates segments in the uppermost IDATA memory space. The segments specified will follow all other segments in the internal data memory space.

µVision2 Control: Options – BL51 Locate – Xdata Range, Xdata.

Description: The XDATA control allows you to specify:

BL51 MYPROG.OBJ CODE(0 - 0x3FF, 0xF800 - 0xFFFF)

To specify the order for segments, you must include the names of the segments separated by commas. The following example will place the ?XD?MOD1 and ?XD?MOD2 segments at the beginning of the XDATA memory:

BL51 MOD1.OBJ,MOD2.OBJ CODE(?XD?MOD1, ?XD?MOD2)

You can also specify the memory location for a segment. The example below will place the ?XD?MOD1 segment at

800h:

BL51 MOD1.OBJ,MOD2.OBJ CODE(?XD?MOD1 (0x800))