TI 54x Assembler - Is it possible to move between T/ASM and A/B registers

Hi all,

I have what should be a simple request that I can't seem to find the
answer to.

In TI 54x assembler, is there an instruction to copy a value directly
from either the T or ASM registers to the A/B accumulator registers?

My motivation is that fixed point math frequently requires a shift
value to be calculated in the A or B accumulators (I dont believe T or
ASM can do arithmetic). Once the shift value is calculated in A or B, I
believe it needs to be copied to the T or ASM registers in order for
the shift to be applied, for example using 'NORM A' or 'LD A, ASM, A'
respectively.

However I can not find a single instruction method of moving the shift
value from A or B to T or ASM in 54x assembly.

My current solution is to use the stack as an intermediate storage
location, for example:
(shift value has been calculated in B)
STL  B, *sp(temp)
LD   *sp(temp), ASM

but this feels inefficient and dirty.

Help clean my code up!

Regards,

Nick

I have just found a solution, although I still think its a bit of a
hack.

Absolute addressing can be used to address a memory mapped register,
therefore allowing a register such as T or ASM to be used as a Smem
parameter.

For example
LD T, B
does not work because T is not a Smem address

But
LD *(0Eh), B
does work because *(0Eh) is a Smem address that points to the memory
mapped location of the T register (see SPRU131G pg 3-27).


This still feels a bit dirty to me, but at least it is just one
instruction. Is there a better method?

Regards,

Nick

Look at the MVMM instruction (Move Memory Mapped Register) (or similarly the
MVDK, MVDM )  I think one of these will do what you need.  Just be careful
of pipeline latencies.

Going from A or B into T is straight forward:
 STLM A,T     ;  T=x
 MPY  y,A     ; A=x*y

Hope this helps

-Shawn



<npelly@gmail.com> wrote in message
news:1109121040.475930.89540@f14g2000cwb.googlegroups.com...
> Hi all,
>
> I have what should be a simple request that I can't seem to find the
> answer to.
>
> In TI 54x assembler, is there an instruction to copy a value directly
> from either the T or ASM registers to the A/B accumulator registers?
>
> My motivation is that fixed point math frequently requires a shift
> value to be calculated in the A or B accumulators (I dont believe T or
> ASM can do arithmetic). Once the shift value is calculated in A or B, I
> believe it needs to be copied to the T or ASM registers in order for
> the shift to be applied, for example using 'NORM A' or 'LD A, ASM, A'
> respectively.
>
> However I can not find a single instruction method of moving the shift
> value from A or B to T or ASM in 54x assembly.
>
> My current solution is to use the stack as an intermediate storage
> location, for example:
> (shift value has been calculated in B)
> STL  B, *sp(temp)
> LD   *sp(temp), ASM
>
> but this feels inefficient and dirty.
>
> Help clean my code up!
>
> Regards,
>
> Nick
>