In SX Microcontrollers, SX/B Compiler and SX-Key Tool, peterverkaik wrote:

@Bean,

Adding 2 words generates

  5488  01B8  0219        ADD dacValue_MSB,adcValue_MSB  ;dacValue = dacValue + adcValue
        01B9  01F7
  5489  01BA  0218        ADD dacValue_LSB,adcValue_LSB 
        01BB  01F6
  5490  01BC  0603        ADDB dacValue_MSB,C           
        01BD  02B7

If adding the MSB parts generates overflow (C set) but adding the LSB parts does not,
then the overflow is not detected.

If the code was changed to

  mov w,adcValue_LSB
  add dacValue_LSB,w
  mov w,adcValue_MSB
  snc
  movsz w,++adcValue_MSB ;leaves C intact
  add dacValue_MSB,w

then we can detect 16bit overflow by testing carry.
This takes the same amount of code.
(code was found on sxlist.com)

regards peter

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