Lpc2000

---- Original Message ----
From: "Guillermo Prandi" <yahoo.messenger@...>
To: <lpc2000@yahoogroups.com>
Sent: Saturday, October 29, 2005 2:22 AM
Subject: [lpc2000] Re: LPC2138FBD64 - not possible to run from Flash
and use IAP?

> Karl, I'm an LPC newbie so please excuse my silly question but, why
> not just...?
>
> void (*CallIAP)(unsigned int *cmd, unsigned int *resp) = 0x7ffffff1;
>
> void My Func()
> {
>   .
>   .
>   CallIAP(cmd, resp);
>   .
>   .
> }
>
> What does the assembler routine you wrote do different from this?

The above works when you have enabled interworking.  I think that Keil
always uses interworking.  GCC only uses it when you enable it
by -mthumb-interwork.

With interworking, the compiler always uses the mode-switching BX
instruction for returns and indirect calls.  (For direct calls it uses a
normal BL, and when the caller and callee are different mode, the linker
then inserts a small piece of code between them that switches mode).  Using
BX for returning often produces less efficient code.

Using the CallIAP assembler routine means that you can avoid
-mthumb-interwork, and only use BX in the single place it is needed, i.e.
when calling the IAP entry point (assuming that the whole program is in ARM
mode).

Karl Olsen