CN101625643B

CN101625643B - Address mapping method of 8051 single chip

Info

Publication number: CN101625643B
Application number: CN2009100592304A
Authority: CN
Inventors: 孙银明
Original assignee: IPGoal Microelectronics Sichuan Co Ltd
Current assignee: IPGoal Microelectronics Sichuan Co Ltd
Priority date: 2009-05-08
Filing date: 2009-05-08
Publication date: 2012-01-04
Anticipated expiration: 2029-05-08
Also published as: CN101625643A

Abstract

The invention discloses an address mapping method of 8051 single chip, wherein the method is characterized in that: LCALL and LJMP instructions are analyzed from absolute address 0000H to the final address in program code one by one and the absolute address CMD_ADD of LCALL and LJMP operations is obtained; and then whether the absolute address exceeds the address range of a first section SEGLEN is judged, when CMD_ADD is equal to or more than SEGLEN, the address exceeds the range, and when CMD_ADD is less than SEGLEN, the address does not exceed the range; and when CMD_ADD exceeds the range of SEGLEN, CMD_ADD is modified into a first SEGLEN address space in integral multiple of section address space SEGLEN. The invention requires no support of hardware to realize address mapping; section size can not be fixed but can be flexibly configured according to system requirement; the quantity of section can not be fixed but can be flexibly configured according to the system requirement.

Description

A kind of 8051 single-chip microcomputer address mapping methods

Technical field

The present invention relates to digital consumption electronic product system, particularly a kind of 8051 single-chip microcomputer address mapping methods.

Background technology

The space, program address of 8051 series monolithics is 64KB (words), and the data address space also is 64KB.The general system that adopts 8051 single-chip microcomputers, the program space all is to be divided into two parts, a part be read-only be that ROM (Read OnlyMemory) is fixing immutable, be used to store important system start-up code; Another part be read-write be PRAM (Program Random Access Memory), data-carrier store RAM (Random Access Memory) is placed on the space, program address, the purpose of this part code is for the expansion of program and upgrading.In the System on Chip/SoC the inside, because the cost of PRAM is high more a lot of than ROM, it is smaller that the PRAM address space all can design.

Actual program code can be bigger than PRAM, so program code need be loaded among the PRAM several times and moves.Real program code is because big more a lot of than PRAM; Generally be stored in outside the System on Chip/SoC; In system operation time, is loaded among the PRAM piecemeal according to the flow direction of instruction and carries out, and can practice thrift expansion and upgrading that system cost also can realize program code easily like this.

For example the size of PRAM is 4KB, and actual program code space requirement 40KB so just need be divided into 10 4KB with program code, according to the ruuning situation of program, is loaded among the PRAM piecemeal and moves.

As shown in Figure 1, the address space of PRAM be fix be 1000H to 1FFFH, size also is fixedly to be 4KB (explain with the 4KB size that here actual can be any size, first 4KB is exactly first section so).The scope in space, program address is that 1000H is the 40KB address space to AFFFH, is divided into 10 sections.When system moves, can be according to the trend of program, every section 4KB is loaded among the PRAM one by one with 10 sections, moves for system.Here just problem has been arranged, in 10 section programs, had only the 1st section the address of address and PRAM the same; Be that 1000H is to 1FFFH; And follow-up 9 sections address is all high than PRAM, and its program directly is loaded into can not be moved among the PRAM, need be with its map addresses to 1000H to 1FFFH.

The hardware mapping method specifies as follows:

8051 space, program address is 64KB; 16 address wire ADD [15:0] are promptly arranged; The address wire of PRAM 4KB space requirement is ADD [0:11]; As long as remaining address wire ADD [15:12] is fixed as 0001H, 2000H just can be mapped to 1000H to the 1FFFH space piecemeal to the address space of AFFFH, and other sector addresses that are about to except that the 1st section all are mapped to the 1st sector address space 1000H to 1FFFH.

Though do the mapping that can realize the address like this, the program code in each section is loaded into the PRAM space can correct execution, does not exceed problem and do not go out current address.But hardware address is mapped with following defective:

1, needs hardware that some address wire is fixed, increase hardware spending, also bring risk to system;

2, the section size fixedly brought of hardware address is also fixing, and the section of adjustment is big or small as required, uses dumb;

3, the fixed number of the section fixedly brought of hardware address is used underaction;

In the system that does not have the mapping of hardware address line, can't use this segmentation loading method.

In 8051 order set, relate to several instructions of specific address, as: LCALL (long call instruction); LJMP (long jump instruction) etc.; LJMP with wherein is an example, and order format is LJMP 1000H (example), and this instruction just might jump to the another one section from a section; Promptly, just do not needed map addresses as long as guarantee the not address of the section of exceeding of similar specific address.The specific address here is meant to be reference with address 0000H only, and address realm is whole 64KB space; Relative address then is to be reference with the present procedure instruction address, and address realm is 2KB.Specific address is not easy control, is easy to exceed the address of a section, and relative address is controlled easily, as long as specific address is done map addresses, has just realized the effect of program address mapping.

In the time of system start-up, the 1st section is loaded into the PRAM space, because the 1st section address with PRAM all is that 1000H is to 1FFFH, so system's operation is no problem; After being loaded into the 2nd section program code among the PRAM, address space is just inequality, and promptly program might exceed 1000H to the 1FFFH space in the address, causes catastrophic effect.Key is that the address is indifferent in the instruction of 8051 major part, promptly at 1000H to 1FFFH or 2000H to 2FFFH, operation can, the instruction relevant with the address also is divided into two types: specific address and relative address.The scope of specific address is whole 64KB, and the scope of relative address is 2KB, so the present invention will be modified to the PRAM address space and realize map addresses relating to the operated address of absolute address instruction in the program space.

Summary of the invention

The present invention provides a kind of 8051 single-chip microcomputer address mapping methods for solving the problems of the technologies described above, and is specially adapted to 8051 systems, the defective that can avoid the hardware address mapping to bring.

Technical scheme of the present invention is following:

A kind of 8051 single-chip microcomputer address mapping methods; It is characterized in that: program code is analyzed LCALL and LJMP instruction (because having only the specific address that might surpass first segment limit that is only of these two instruction manipulations) one by one from specific address 0000H to a last address; And obtain the specific address CMD_ADD of LCALL and LJMP operation, judge then whether this specific address surpasses first section address realm SEGLEN:

If CMD_ADD＞=SEGLEN, the address exceeds so;

If CMD_ADD＜SEGLEN thinks that then the address does not exceed;

When CMD_ADD exceeds the SEGLEN scope, CMD_ADD is modified to first section SEGLEN address space according to the integral multiple of sector address space S EGLEN, i.e. the address space at PRAM place.Every section program code moves needed specific address space and can not surpass first section PRAM address space like this, and the program of each section can be loaded into the PRAM space and normally moves so, reaches the purpose of map addresses.

The formula of address modification is:

NEW_ADD＝CMD_ADD-(N-1)*SEGLEN

Wherein, the specific address of instruction manipulation in the CMD_ADD representation program code, NEW_ADD is amended address, and N is the segment number at program code place, and every section size is SEGLEN.

In program code, replace original C MD_ADD at last, just realized map addresses with NEW_ADD.

Beneficial effect of the present invention is following:

The present invention can not need the support of hardware, realizes map addresses; Canned paragraph is not big or small, according to system's needs flexible configuration; The quantity of canned paragraph not is according to system's needs flexible configuration.

Description of drawings

Fig. 1 is the address space synoptic diagram of PRAM

Embodiment

A kind of 8051 single-chip microcomputer address mapping methods; Program code is analyzed LCALL and LJMP instruction one by one from specific address 0000H to a last address; And obtain the specific address CMD_ADD of LCALL and LJMP operation, judge then whether this specific address surpasses first section address realm SEGLEN:

If CMD_ADD＞=SEGLEN, the address exceeds so;

If CMD_ADD＜SEGLEN thinks that then the address does not exceed;

The formula of address modification is:

NEW_ADD＝CMD_ADD-(N-1)*SEGLEN

For example: certain instruction manipulation specific address CMD_ADD is 2500H in the program code; Amended address is NEW_ADD; The segment number N at the program code place of this operation is the 2nd section, and every section big or small SEGLEN is 1000H, and the address space of first section PRAM is that 1000H is to 1FFFH.Because CDM_ADD has surpassed the address space of PRAM, need shine upon NEW_ADD and replace CMD_ADD, according to formula:

NEW_ADD＝CMD_ADD-(N-1)*SEGLEN

CMD_ADD＝2500H

SEGLEN?＝1000H

N ＝2

Calculate NEW_ADD=1500H.

NEW_ADD is in PRAM address 1000H within the 1FFFH scope, can be in PRAM control operation.According to this formula, with definitely all revising of all instruction manipulations in this section, program code just can normally be carried out in the PRAM space so, has realized the software address mapping.

This method does not need the support of hardware address mapping, and N (hop count amount) and SEGLEN (section size) in can the flexible configuration formula, can in the system that did not use the sector address mapping, use yet, and has successfully solved the defective that hardware address shines upon.

Said method is applicable to 8051 order set.

For example: in 8051 control system of a hardware address mapping, the gross space size of program code is 64KB, is divided into 8 sections, and every section size is 8KB.Address space from 0000H to 1FFFH is read-only code ROM, the address space of the 1st section PRAM be 2000H to 3FFFH, the program code in follow-up 6 sector address spaces need be loaded into the PRAM space piecemeal and carry out.

Hardware circuit is fixed as 001H with the ADD [15:13] among 16 address wire ADD [15:0], just can not surpass the address space of PRAM so from the address that 16 address wires are sent, and promptly follow-up 6 sections program code can be loaded into the operation of PRAM address space.Though realized map addresses like this, need hardware circuit fixed address line, the size of section is also immutable with the quantity of section.

Use the method for software address mapping following:

Always having 6 sector addresses needs mapping, and the scope of N is 1 to 6, the big or small SEGLEN=2000H of section, so according to formula:

NEW_ADD＝CMD_ADD-(N-1)*2000H

With N from 1 to 6; From code, find whole specific address CMD_ADD; Calculate the NEW_ADD that is used for replacing respectively, through map addresses piecemeal, just can be all surpass the specific address in PRAM space in the program code; All be mapped to the PRAM address space, thereby guarantee that every section program code can normally carry out in the PARM space.

In 8051 systems that do not consider sectional address mapping, because function increases and revises, need extender code address space, utilize this segmentation mapping method, also can successfully realize, get a desired effect, for example:

In one 8051 system, read-only program ROM address space be 0000H to 7FFFH, promptly size is 32KB.But the space of loading section PRAM be 8000H to 9FFFH, promptly size is 8KB.Owing to need the expanding system function to increase code; Can only be able to loading department increase; The 8KB address space of PRAM can hold any more too much function code so, does not have map addresses on the hardware yet, does not promptly consider to load respectively use with a plurality of 8KB program segments.The mapping method that this paper proposed so just can solve this problem.

The size of PRAM is 8KB, and this part address space can be as the address space (reality as required can be littler than 8KB) of first section SEGLEN.

Suppose only to use back 4KB space among the PRAM as SEGLEN, so first section address space be 9000H to 9FFFH, i.e. SEGLEN=1000H

Suppose that the program size after the interpolation function is 19KB; Be far longer than the 8KB space of PRAM; What need increase so is that the hop count of unit is (19KB-8KB)/4KB round numbers N=3 with SEGLEN; Add among the PRAM first section N=4 so, promptly except that original PRAM 8KB, need to increase by the section of 3 4KB.

Can obtain from above

SEGLEN＝1000H

N ＝4

With the program code of 19KB according to formula:

NEW_ADD＝CMD_ADD-(N-1)*SEGLEN

N from 1 to 4; From code, find whole specific address CMD_ADD; Calculate the NEW_ADD that is used for replacing respectively; Just can all be mapped to the SEGLEN address space, thereby guarantee that every section program code can normally carry out in the SEGLEN space all surpass the specific address in SEGLEN space in the program code.System when operation is that carry out in the SEGLEN space with the back 4KB that each section is loaded into PRAM respectively as required, just can hold the code above 8KB, successful solution this system problem.

Claims

1. single-chip microcomputer address mapping method; It is characterized in that: program code is analyzed LCALL and LJMP instruction one by one from specific address 0000H to a last address; And obtain the specific address CMD_ADD of LCALL and LJMP operation, judge then whether this specific address surpasses the first sector address space S EGLEN:

If CMD_ADD＞=SEGLEN, the address exceeds so;

If CMD_ADD＜SEGLEN, then the address does not exceed;

When CMD_ADD exceeds the SEGLEN scope, CMD_ADD is modified to the first sector address space S EGLEN according to the integral multiple of sector address space S EGLEN;

The formula of said address modification is:

NEW_ADD＝CMD_ADD-(N-1)*SEGLEN

Wherein, the specific address of instruction LCALL and LJMP operation in the CMD_ADD representation program code, NEW_ADD is amended address, and N is the segment number at program code place, and promptly said integral multiple is meant N-1 doubly, and every section size is SEGLEN.

2. according to the said a kind of 8051 single-chip microcomputer address mapping methods of claim 1, it is characterized in that: after the address modification, in program code,, realize map addresses with NEW_ADD replacement original C MD_ADD.