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

You'll have to synthesize a 24-bit value from a byte and a Word.  Let's say you do this:

[code]calHigh         VAR     Byte                    ' bits 16 - 23
calLow          VAR     Word                    ' bits  0 - 15[/code]
The trick is shifting from one to the other -- this is tricky in high-level SX/B because the >> and << operators clear the Carry bit which is what we use to get a bit from one byte to the next.  Let's assume the values are arriving MSB-first after the clock line goes high.  You might have a loop like this:

[code]Get_Cal_Bits:
  FOR idx = 0 TO 23
    DO WHILE ClockPin = 0
    LOOP
    calHigh = calHigh << 1
    calHigh.0 = calLow.15
    calLow = calLow << 1
    calLow.0 = DataPin
    DO WHILE ClockPin = 1
    LOOP    
  NEXT[/code]
If you look at the compiler output for the shift opeators you'll see that the Carry gets cleared first.  This is why we have to shift and then copy a bit from one element to the other.  In assembly, it's a little easier because the Carry helps us:

[code]Get_Cal_Bits:
  FOR idx = 0 TO 23
    ASM
      JNB   ClockPin, @$
      MOVB  C, DataPin
      RL    calLow_LSB
      RL    calLow_MSB
      RL    calHigh
      JB    ClockPin, @$
    ENDASM 
  NEXT[/code]
As you can see, we copy the Data pin into the Carry bit and the the left shift (RL) instructions move everything through (right to left).  I don't know if this will help you but, perhaps, it will give you some insight into getting 24 bits from the caliper.

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