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MAEC TOOL NEWS:
MAECT-NC308WA-010916D
NC308WA, NC30WA, AS308, and AS30
Precautions
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Please take note of the following problem in using C compilers (with an assembler and integrated development environment) NC308WA and NC30WA; and assemblers AS308 and AS30 for the M16C family MCUs:
- On the function of optimizing branch instructions
- Versions Concerned
| C compiler for the M16C/80 series MCUs |
: NC308WA V.1.00 Release 1 -- V.3.10 Release 3 |
| C compiler for the M16C/60 and M16C/20 series MCUs |
: NC30WA V.1.00 Release 1 -- V.4.00 Release 2 |
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| Assembler for the M16C/80 series MCUs | : AS308 V.1.00 Release 1 -- V.2.00 Release 1 |
| Assembler for the M16C/60 and M16C/20 series MCUs |
: AS30 V.1.00 Release 1 -- V.3.20 Release 1 |
- Description
When the assembler concerned performs optimization of branch instructions, an error message "Value is out of range" may appear at the line where an unconditional branch instruction (JMP) resides.
- Conditions
- This problem occurs if the following three conditions are satisfied:
- (1) As a result of optimization, a short-jump instruction "JMP.S" is generated for each of the two successive unconditional branch instructions.
- (2) Between the second unconditional branch instruction and its destination is described an ".ALIGN" directive to correct the address to even.
- (3) The alignment places the destination of the second unconditional branch instruction at the address indicated by the program counter (PC)+10.
- Example
In a source file written in assembler language
------------------------------------------------------------------------
.section prg,code,align
jmp label1
.byte 1,2,3,4
label1:
.byte 1,2,3
jmp label2 ; At this line an error message appears.
.byte 1,2,3,4
.byte 1,2,3,4
.align ; Condition (2) (Here is made alignment.)
label2: ; Condition (3)
.end
------------------------------------------------------------------------
- Workaround
Disable the generation of a short-jump instruction (JMP.S) for the unconditional branch instruction that causes the error by describing a JMP.S-generation control directive ".SJMP".
- 5.1 In a Source File Written in Assembler Language
-----------------------------------------------------------------------
.section prg,code,align
jmp label1
.byte 1,2,3,4
label1:
.byte 1,2,3
.sjmp off ; Generation of a JMP.S instruction disabled.
jmp label2
.sjmp on ; Generation of a JMP.S instruction enabled.
.byte 1,2,3,4
.byte 1,2,3,4
.align
label2:
.end
-----------------------------------------------------------------------
- 5.2 In a Source File Written in C Language
Suppose this type of error arises within an if-else construct.
-------------------------------------------------------------------------
func( )
{
asm(" .sjmp off "); /* Generation of a JMP.S instruction disabled */
if(xxxxx)
......
else
.......
asm(" .sjmp on "); /* Generation of a JMP.S instruction enabled */
}
-------------------------------------------------------------------------
- Schedule of Fixing the Problem
We plan to fix this problem in our next release.
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