This is the Atmel WAVRASM Bug
It is me, or this compiler has a bug when calculating the .db directive addressing?
The problem appeared in a long run, I reduced to the minimum exercise so it is possible to duplicate and exercise.
Follows the assembly code and the compilation listing result:
Source:
It is me, or this compiler has a bug when calculating the .db directive addressing?
The problem appeared in a long run, I reduced to the minimum exercise so it is possible to duplicate and exercise.
Follows the assembly code and the compilation listing result:
Source:
| CODE |
.cseg Ldi R30,(MSG001) Ldi R30,(MSG002) Ldi R30,(MSG003) Ldi R30,(MSG004) Ldi R30,(MSG005) Ldi R30,(MSG006) MSG001: .DB 1,"A" MSG002: .DB 1,"A" MSG003: .DB 1,"A" MSG004: .DB "A",1 MSG005: .DB "A",1 MSG006: .DB "A",1 |
Listing:
| QUOTE |
.cseg 000000 e0e6 Ldi R30,(MSG001) 000001 e0e8 Ldi R30,(MSG002) 000002 e0ea Ldi R30,(MSG003) 000003 e0ec Ldi R30,(MSG004) 000004 e0ed Ldi R30,(MSG005) 000005 e0ee Ldi R30,(MSG006) 000006 4101 MSG001: .DB 1,"A" 000007 4101 MSG002: .DB 1,"A" 000008 4101 MSG003: .DB 1,"A" 000009 0141 MSG004: .DB "A",1 00000a 0141 MSG005: .DB "A",1 00000b 0141 MSG006: .DB "A",1 |
Problem definition:
Note the line 000000, it shows the correct .db directive address at label MSG001, when assembling e0e6.
Lets open the instruction:
e... means LDI (Load Immediate)
..e. means into register 0Eh from the 16-31 package (R30).
.0.6 means label is at address (low) 06h.
E0D8
The E means Instruction LDI (load immediate)
The D means the 13th register from 16-31 package
The 08 means memory source address.
Note the line 000001, it is already incorrect. Decompose the e0e8 as show above, you will see it is already pointing to
address 08h instead of 07h, the correct MSG002 label address (skiped 1 byte).
Note the line 000002, it still pushing the error, now its e0ea is trying to say the MSG003 is located at address 0Ah, what is double incorrect, MSG003 is at 08h (skiped 1 byte).
Note the line 000003, e0ec shows also incorrect MSG004 position (skiped 1 byte)
Now note lines 000004 and 000005, it is not jumping the extra byte as the previous lines, but it still with an offset error pushed from the previous.
Everything goes wrong whenever you use a directive .DB with a number before a text.
In this case, source code MSG001, 002 and 003 are using .DB 1,"A" (number before text), while MSG004, 005 and 006, are using .DB "A",1 (number after text).
If in the directive .DB you use 1,$41 instead of 1,"A", it will generate exactly the same compiled data bytes, but the address calculation will be correct.
The problem is isolated to when using at least one numeric digit before a quoted text in the .db directive.
Anyone already saw this flaw? or it is me?
The correct listing should be:
| QUOTE |
.cseg 000000 e0e6 Ldi R30,(MSG001) 000001 e0e7 Ldi R30,(MSG002) 000002 e0e8 Ldi R30,(MSG003) 000003 e0e9 Ldi R30,(MSG004) 000004 e0ea Ldi R30,(MSG005) 000005 e0eb Ldi R30,(MSG006) 000006 4101 MSG001: .DB 1,"A" 000007 4101 MSG002: .DB 1,"A" 000008 4101 MSG003: .DB 1,"A" 000009 0141 MSG004: .DB "A",1 00000a 0141 MSG005: .DB "A",1 00000b 0141 MSG006: .DB "A",1 |
Final note:
If using single quote (') instead of double (") around the text, it works correctly, so, why double quotes generate the problem?
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Wagner Lipnharski - Director - wagner@ustr.net
UST Research Inc. - Orlando - FL - http://www.ustr.net