When you use it through the DMA, you're explicitly using the multiplier. When you enable the flag, gcc uses the multiplier to not only perform arithmetic operations but also to compute memory addresses in variable assignments. When interrupts occur, there is often a conflict in the multiplier's use, and random memory segments are overwritten (bad!)
Since you're not using a compiler flag, then the hardware multiplier use by gcc is disabled, which means there isn't any competition for the resource. If you enable the flag, gcc doesn't know if the DMA is using it or if it should use it for memory address calculation and I guarantee disastrous results. -Joe On 7/19/06, Matthew J Whelan <[EMAIL PROTECTED]> wrote:
Joe, I have been using the Hardware multiplier through DMA transfers for a while now to implement digitial filtering. I have never used a compiler flag to do this, but everything seems to be working fine. Is there any reason to believe that there might be errors if I am using the multiplier without this compiler flag? Thanks, Matt [EMAIL PROTECTED] wrote: ----- To: "Matthew J Whelan" <[EMAIL PROTECTED]> From: "Joe Polastre" <[EMAIL PROTECTED]> Sent by: [EMAIL PROTECTED] Date: 07/19/2006 05:15PM cc: tinyos-help@millennium.berkeley.edu Subject: Re: [Tinyos-help] MSP430 Hardware Multiplier Compiler Flag mspgcc's implementation of the hardware multiplier arbitration is very buggy. I would not recommend using it. Unfortunately no one here is a compiler expert, so it still hasn't been fixed. -Joe On 7/19/06, Matthew J Whelan <[EMAIL PROTECTED]> wrote: > > > Hi, > > > > I have found a previous post that states that I need to use the compiler > option > > -mforce-hwmul to properly use the hardware multiplier on the MSP430. What I > did was > > add the line NESC_FLAGS+=-mforce-hwmul to my makefile. However, now I see > both -mforce-hwmul as well as -mdisable-hwmul in the compiler output. What > is the proper way to add this flag so that the multiplier can be used? > > > > Thanks > > Matt > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@Millennium.Berkeley.EDU > https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > >
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