[sdiy] uC with mul

[mikko.a.helin at nokia.com]

Software 8x8 -> 16 multiplication on AVR takes 34 cycles, is that really too
slow? For MIDI applications with 7 bit control word even less (30 I think).

-Mikko

> -----Original Message-----
> From: ext John Loffink [mailto:jloffink at austin.rr.com]
> Sent: 30. December 2001 17:08
> To: Byron G. Jacquot; synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] uC with mul
> 
> 
> The multiply cycle on the 68HC16 is 8 cycles.  Other micros 
> do have the
> multiply instruction, usually multi cycle instructions.  
> These might be
> good enough depending on your application, particularly for low
> frequency stuff like note generation, envelopes, LFOs, 
> control sources,
> etc., but for anything related to analog synthesis it's 
> generally better
> to have 12-16 bits of resolution to avoid stair-stepping.
> 
> John Loffink
> jloffink at austin.rr.com 
> 
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Byron 
> G. Jacquot
> Sent: Saturday, December 29, 2001 10:29 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] uC with mul
> 
> >Motorola M68HC16 microcontroller series has a 16 bit
> >multiplier/accumulator.
> 
> The "little brother" 68HC11 could also do 8*8 multiply, and 
> (IIRC) 16/8
> division.  They were both kinda slow.  I think a multiply took 12
> cycles,
> and the divide something amazing like 42.
> 
> Byron Jacquot
>