• State Not Answered
  • Locked Locked
  • Replies 5 replies
  • Subscribers 22 subscribers
  • Views 1233 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Memory copy - xhuge and near model types

Iggy Pop

Hello all,

may you give me an explanation of following piece of code (target is ST10F276):

U8 ndata * Dest;
U8 xhuge * Source;
register U16 wTemp;

while([condition]) {
.....
wTemp = *((U16 xhuge *) Source);
*((U8 ndata *) (Dest++)) = *((U8 ndata *) & wTemp);
*((U8 ndata *) (Dest++)) = *((U8 ndata *) & wTemp + 1);
Source += 2;
.....
}


I understand that read operation (instructions) of data from xhuge pointer is very slow - therefore complete word is read out and stored into any register given by compiler.

But what is an advantage of write per Bytes? AFAIK the processor ST10F276 has 16bit wide bus, has not?

Thanks for your hints in advance,

Best regards
Iggy

Parents
  • 0 in reply to Mike Kleshov

    Perhaps a reason of this approach is:

    premise: Word (16bit) storing into Dest always begins at even address (= default feature of such processor).

    If Source starts at odd address, then only one Byte (not whole Word - 16bit) is copied into 1st Byte of destination Word. Afterwards per-Byte coyping must be performed, otherwise one Byte gap (2nd Byte of 1st destination Word) occurs in the Dest buffer.

Reply
  • 0 in reply to Mike Kleshov

    Perhaps a reason of this approach is:

    premise: Word (16bit) storing into Dest always begins at even address (= default feature of such processor).

    If Source starts at odd address, then only one Byte (not whole Word - 16bit) is copied into 1st Byte of destination Word. Afterwards per-Byte coyping must be performed, otherwise one Byte gap (2nd Byte of 1st destination Word) occurs in the Dest buffer.

Children
No data