#32 - Symbolic Address

#L32

Q: What is the Symbolic Addressing Mode?

Symbolic Addressing in Program Mode

The vector comment field can now (ETSNT, Version 5.3 and higher) be employed for symbolic addressing. Certain rules are enforced, primarily to extend program mode to QuickLoad in AutoTest. This beta feature is invoked by the SpS keyword 'AllowSymbolicAddressInComments'. The following Rules & Regulations apply:

1. The first comment line (vector 0 comment) must start with the keyword '_PrgCmd', indicating that comments have program commands.

2. First line of program must be PAGE 0, and second line of program must be JMP 2. Note: these program commands are automatically generated (the aforementioned keyword does the invocation).

3. Vector 2 comment must begin with ':BEGIN' (which is a 'label' preceded by the key delimiter ':'). Again, the ETSNT generates it automatically.

4. Last vector comment indicates last vector by the keyword '_LastVec' - inserted automatically. This, however, is not a label; just a comment convenient when the feature of comment search is implemented. Similarly, the StopVector will have the comment '_StopVector' inserted. (CommentSearch makes these comments an operating convenience).

5. The comment for the last vector minus 1 must begin with ':END'. This label is also generated automatically. Between 'BEGIN' and 'END' (inclusive) is the program space accessible as references by the various branch instructions of the program.

By these five simple rules, of which conformation and/or generation is automatic, lies the foundation for applying program mode to QuickLoad in AutoTest. In addition, symbolic addressing must be adhered to throughout. While we can run vector programs where symbolic programming is only adhered to partially, such programs cannot be applied to AutoTest if QuickLoad is desired.

The syntax for the program itself is simple and summarized by the following rules:

A. Only branch instructions associated with labels (JMP, CJMP, CALL, CCALL) need to be considered for programming in the comment field. The LOOP instruction has by our new convention no label associated with it. It is called LOOP@, indicating looping to itself. If the user desires the old convention, we have provided equivalency by invoking the SpS keyword 'UseOldProgramRules'.

B. To assign a symbolic label to a branch instruction, just type a '$ ' followed by '=', '+', '-', or LabelName. The '=' signifies branch to itself (e.g. waiting for a condition), while + and - signifies relative addressing - that is, relative to the location of the branch instruction (the +/- will be followed by an integer which determines the relative branch). LabelName is any label of any size, of which the first 15 characters have significance (i.e. 16'th character and characters beyond are ignored).

C. The LabelName associated with a vector must appear in the comment field and be preceded by the delimiter ':'. The label name itself could be any alphanumeric string of which the first fifteen characters have significance.

The following vector display illustrates the concept:


Before pressing Run:

           |              |                    |
  Vector   |              |                    |
  Address  |   Program    |                    |  Comments
   (Hex)   |              |                    |
           |              |    Split Cycle     | 
===============================================
   00000   |  NOOP        | 00000000 00000000  |  _PrgCmd
   00001   |  NOOP        | 00000001 00000001  |
   00002   |  LOADX    00 | 00000002 00000002  |
   00003   |  LOAD   0FFF | 00000003 00000003  |
   00004   |  NOOP        | 00000004 00000004  |
   00005   |  NOOP        | 00000005 00000005  |  just a comment
   00006   |  NOOP        | 00000006 00000006  |
   00007   |  CJMP   0000 | 00000007 00000007  |  $Alabel  more comment
   00008   |  JMP    0000 | 00000008 00000008  |  $+3 ; jump to adr + 3
   00009   |  NOOP        | 00000008 00000008  |
   0000A   |  NOOP        | 00000008 00000008  |  :Alabel
   0000B   |  NOOP        | 00000008 00000008  |
   0000C   |  LOOP@       | 00000008 00000008  |
   0000D   |  NOOP        | 00000008 00000008  |
   0000E   |  NOOP        | 00000008 00000008  |
   0000F   |  NOOP        | 00000008 00000008  |
   00010   |  NOOP        | 00000008 00000008  |


After pressing the Run button, the display changes to:

           |              |                    |
  Vector   |              |                    |
  Address  |   Program    |                    |  Comments
   (Hex)   |              |                    |
           |              |    Split Cycle     |
===============================================
   00000   |  PAGE     00 | 00000000 00000000  |  _PrgCmd
   00001   |  JMP    0002 | 00000001 00000001  |
   00002   |  LOADX    00 | 00000002 00000002  |  :BEGIN  
   00003   |  LOAD   0FFF | 00000003 00000003  |
   00004   |  NOOP        | 00000004 00000004  |
   00005   |  NOOP        | 00000005 00000005  |  just a comment
   00006   |  NOOP        | 00000006 00000006  |
   00007   |  CJMP   000A | 00000007 00000007  |  $Alabel  more comment
   00008   |  JMP    000B | 00000008 00000008  |  $+3 ; jump to adr + 3
   00009   |  NOOP        | 00000008 00000008  |
   0000A   |  NOOP        | 00000008 00000008  |  :Alabel
   0000B   |  NOOP        | 00000008 00000008  |
   0000C   |  LOOP@       | 00000008 00000008  |
   0000D   |  NOOP        | 00000008 00000008  |
   0000E   |  NOOP        | 00000008 00000008  |  _StopVec
   0000F   |  NOOP        | 00000008 00000008  |  :END 
   00010   |  NOOP        | 00000008 00000008  |  _LastVec

Note: the line with '_StopVec', indicating the Stop Vector, which is not the same as Last Vector. The ETSNT warns the user of this deviation from the rules, but allows it to run anyway. The warning message will only appear one time during the entire session.

Importantly, this real time compilation (perhaps more correctly assembly) slows down the running process as a function of several factors, primarily the number of lines of comments and the total number of comments. While, the translation will only occur as required (a subsequent pressing of the RUN button will skip the compilation process), it slows down the run when a comment is added or changed. We understand the essence of the element of time during the debugging process, and have done our utmost to mitigate this timing predicament. However, assembly is never done instantly and the price to pay may warrant temporary deviations from the norm. Do this by changing the aforementioned keyword '_PrgCmd' to 'PrgCmd', and the software will behave as if no compilation existed. Then, when the job nears completion, you can reintroduce '_PrgCmd' and finish off the job with a program well documented and easily enhanced and modified.

Also See:

Q'nApp #L7: Vector Looping
Q'nApp #L8: Pattern Matching
Q'nApp #L15: Special Script

QL32.zip is a zipped Word file of this Q'nApp.

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