TMS320F280049C: what's the difference between @ACC and ACC

jjl3 said:

   for example:   MOVL XAR1,@ACC                            

                          MOVL XAR1,ACC 

Please refer to http://www.ti.com/lit/spru430

In the addressing modes section, for 32-bit Register Addressing Modes -  there is this note:

Note: When writing assembly code, the “@” symbol in front of the register is optional. For example:
“MOVL ACC,@P” or “MOVL ACC,P”. The disassembler will use the @ to indicate operands that are
“loc16” or “loc32”. For example, MOVL ACC, @P is the MOVL ACC, loc32 instruction and MOVL @ACC,
P is the MOVL loc32, P instruction.

For this specific example, this means:

MOVL XAR1, @ACC:

• Corresponds to the instruction MOVL XARn, loc32 = Store loc32 in the auxiliary register n   
• The @ indicates that the 2nd operand is not tied to a specific register
• In this case loc32 operand could be registers other than ACC. 
• The opcode of this instruction includes a field for which axillary register is used (XARn) and which 32-bit location is used (loc32). 
• It does not include the option for a condition to be specified.

MOVL XAR1, ACC

• Corresponds to the instruction MOVL loc32, ACC, CND = Conditional store of the ACC
• In this case ACC is fixed - it cannot be any other register 
• This form allows for a condition (CND) to be used.  The opcode includes a field for this condition. 

If no condition is required then the first form is better because it is a 16-bit opcode vs a 32-bit opcode for the conditional move. 

jjl3 said:

MOV AL,*+XAR4[#6] ; AL = InFilter
MOV AH,*+XAR4[#7] ; AH = InFilter2
SETC AMODE
MOVL *+XAR6[AR1%++],ACC    ; Store new inputs

for the highlighted sentence,

Normally it should be associated with RPT #N,

but there is not "RPT" here, so what's the means here?

If there is no RPT instruction, then the instruction is only executed once.  The circular addressing mode is described in  http://www.ti.com/lit/spru430 section 5.6.3 - in this case AMODE == 1. 

Regards

Lori

thanks!