title: Multiplication two 32-bit SIGNED numbers with Addition and Shifting
body: <p>I need to multiply two 32-bit SIGNED numbers using addition and shifting and get 64-bit number stored in memory locations <code>$0408-$040F</code> . This two numbers are stored in 8-bits memories.</p>
  
  <pre><code> movb #$1F, $0400 ; the first number is $1F230001
   movb #$23, $0401
   movb #$00, $0402
   movb #$01, $0403
   movb #$F8, $0404 ; the second number is $F8012346
   movb #$01, $0405
   movb #$23, $0406
   movb #$46, $0407
  </code></pre>
  
  <p>I know how to multiply two 8-bits numbers with addition and shifting but I dont know how to go on with the others. I used an 16-bit Accumulator-D (accumulator-A 8bits MSB, accumulator-B 8bits LSB).</p>
  
  <p>I am using CPU12: <a href="http://www.freescale.com/files/microcontrollers/doc/ref_manual/CPU12RM.pdf" rel="nofollow noreferrer">Reference Manual</a></p>
  
  <p>Can you help me please, guide me or show me how to do it please? Thank you, I spent much time on this but I don't know how to do it with 32-bits numbers.</p>