Programmable controller having a stored program with both machine language instructions and source code data

• US 5,287,548 A
• Filed: 02/29/1988
• Issued: 02/15/1994
• Est. Priority Date: 02/29/1988
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Original Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Inventors: Rischar, Charles M., Toma, Jack F., Kalan, Michael D., Sepsi, Robert R., Flood, Mark A.
• Primary Examiner(s): Kulik, Paul V.
• Application Number:
  US07/161,484
• Time in Patent Office: 2,178 Days
• Field of Search: 364/200, 364/902, 364/200 MS File, 364/900 MS File, 364/147, 364/191-193, 371/19, 395/700
• US Class Current: 700/18
• CPC Class Codes: G05B 19/056 Programming the PLC
• CPC Class Codes: G05B 2219/13118 Decompiler, translate machine code to hll, reverse processing, easy modification
• CPC Class Codes: G05B 2219/13144 GUI graphical user interface, icon, function bloc editor, OI operator interface
• CPC Class Codes: G05B 2219/15059 Floating point coprocessor
• CPC Class Codes: G05B 2219/15127 Bit and word, byte oriented instructions, boolean and arithmetic operations

Abstract

A programmable controller governs the operation of a piece of equipment by executing machine language instructions compiled from a ladder diagram type control program. The control program as stored in the controller includes not only compiled machine language instructions, but also a tokenized version of the source code from which certain machine language instructions were compiled. The source code is provided only for those portions of the machine language program which cannot be easily decompiled to produce the corresponding source code. This program storage facilitates subsequent editing of the stored program via a terminal connected to the programmable controller. During the editing process, the original ladder diagram can be reconstructed from a combination of the machine language instructions and the tokenized version of the source code. In doing so, the machine language instructions, which have a one-to-one correspondence with the source code instructions, are decompiled using conventional techniques. However, the tokenized version of the source code is used to recreate the portions of the ladder diagram for which each machine language instruction does not have a unique one-to-one correspondence with a source code instruction. This program storage technique enables the control program to be easily edited using the version stored in the programmable controller without requiring access to the original source code from which the program was compiled.

Claims

1. In a programmable logic controller for use in executing an object code control program including a plurality of contiguous program data sectors which correspond to sequential program steps and which include a first section containing general purpose processor instructions and a second section containing tokenized source code information statements for accurately reconstructing source code instructions corresponding to said general purpose processor instructions for program editing purposes, a method for processing said control program at run time for control execution and during program decompiling for full source code reconstruction comprising the steps of:

A) processing each of said control program sectors at run time by;

1) executing said general purpose processor instructions in the first section in each of said sectors, and

2) jumping over said tokenized source code information statements in the second section in each of said sectors; and

B) processing each of said control program sectors during decompiling by;

1) skipping over said general purpose processor instructions in the first section in each of said sectors, and

2) generating source code instructions from said tokenized source code information statements in the second section of each of said sectors.

2. The method of claim 1, wherein said step of jumping over said source code information is initiated with a jump instruction (JMP) at the end of said first sections.

3. The method of claim 1, wherein said step of skipping over said general purpose instructions is initiated with a stop execution instruction (STP) in said first section which specifies an offset to a corresponding third section.

4. The method of claim 1, wherein said program sectors correspond to ladder rungs in a ladder language industrial control program.

5. In a programmable logic controller for use in executing an object code control program including a plurality of contiguous program data sectors which correspond to sequential program steps and which include a first section containing special purpose co-processor instructions having one-to-one relationship with source code instructions, a second section containing general purpose co-processor instructions and a third section containing source code information for accurately reconstructing source code instructions corresponding to said general purpose co-processor instructions for program editing purposes, a method for processing said control program at run time for control execution and during program decompiling for full source code reconstruction compromising the steps of:

A) processing each of said control program sectors at run time by;

1) executing said special purpose co-processor instructions in the first section in each of said sectors,

2) executing said general purpose co-processor instructions in the second section in each of said sectors, and

3) jumping over said source code information in the third section in each of said sectors; and

B) processing each of said control program sectors during decompiling by;

1) generating source code instructions from said special purpose co-processor instructions in the first section in each of said sectors,

2) skipping over said general purpose co-processor instructions in the second section in each of said sectors, and

3) generating source code instructions from said source code information in the third section of each of said sectors.

6. The method of claim 5, wherein said step of jumping over said source code information is initiated with a jump instruction (JMP) at the end of said second sections.

7. The method of claim 5, wherein said step of skipping over said general purpose instructions is initiated with a stop execution instruction (STP) in said first section with specifies an offset to a corresponding third section.

8. The method of claim 5, wherein said program sectors correspond to ladder rungs in a ladder language industrial control program.

9. The method of claim 5, wherein said source code information in said third sections comprises tokenized source code information statements.

10. The method of claim 5, wherein the ends of said third sections containing tokenized source code instruction statements are designated by fixed instruction statements.

11. The method of claim 5, wherein said special purpose co-processor instructions comprise bit co-processor instructions.

12. In a programmable logic controller for use in executing an object code control program including a plurality of contiguous program data sectors which correspond to sequential program steps and which include a first section containing special purpose co-processor instructions having one-to-one relationships with source code instructions, a second section containing general purpose co-processor instructions and a third section containing source code information for accurately reconstructing source code instructions corresponding to said general purpose co-processor instructions for program editing purposes, a system for processing said control program at run time for control execution and during program decompiling for full source code reconstruction comprising:

A) means for processing each of said control program sectors at run time by;

1) executing said special purpose co-processor instructions in the first section in each of said sectors,

2) executing said general purpose co-processor instructions in the second section in each of said sectors, and

3) jumping over said source code information in the third section in each of said sectors; and

B) means for processing each of said control program sectors during program decompiling by;

1) generating source code instructions from said special purpose co-processor instructions in the first section in each of said sectors,

2) skipping over said general purpose co-processor instructions in the second section in each of said sectors, and

3) generating source code instructions from said source code information in the third section of each of said sectors.

13. The system of claim 12, wherein the functional step of jumping over said source code information is initiated with a jump instruction (JMP) at the end of said second sections.

14. The system of claim 12, wherein the functional step of skipping over said general purpose instructions is initiated with a stop execution instruction (STP) in said first section which specifies an offset to a corresponding third section.

15. The method of claim 12, wherein said program sectors correspond to ladder rungs in a ladder language industrial control program.

16. The method of claim 12, wherein said source code information in said third sections comprises tokenized source code instruction statements.

17. The method of claim 16, wherein the ends of said third sections containing tokenized source code instruction statements are designated by fixed instruction statements.

18. The method of claim 12, wherein said special purpose co-processor instructions comprise bit co-processor instructions.