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Use of RRC (Rotate right through carry) in Keil

Tom Leys

The 8051 family of microcontrollers has a very useful assembly instruction RRC. This instruction rotates carry into the MSB of the given register, shifts that register right by 1, and carry becomes equal to what used to be the LSB of the register.

  bit NewCarry;
  unsigned char Data;

  NewCarry = Data & 0x01;
  Data = (Data >> 1);
  if (Carry){
    Data = (Data | 0x80);
  }
  Carry = NewCarry;
Basically it does the above, but all in one instruction. I was wondering what the easiest way to include this in my code was. What I want to do is to read a microcontroller pin into carry, shift it into a data byte, and then use the bit that shifts off as an exit condition. Is there an easy way to include a single assembly instruction in Keil? Perhaps a Intrinsic function?

Thanks

-Tom

Parents
  • 0 in reply to Tom Leys

    would be the ability to compile .asm functions inline

    Whaddayamean "would be"? This ability exists. Guess what: it's even documented. And supported by the IDE. The fact that you don't appear to know that strongly suggests you complain publically before bothering to actually break open the documentation. That's a bad habit.

    Inline assembly does have some drawbacks, but those are largely inevitable, given the way Keil tools are designed.

Reply
  • 0 in reply to Tom Leys

    would be the ability to compile .asm functions inline

    Whaddayamean "would be"? This ability exists. Guess what: it's even documented. And supported by the IDE. The fact that you don't appear to know that strongly suggests you complain publically before bothering to actually break open the documentation. That's a bad habit.

    Inline assembly does have some drawbacks, but those are largely inevitable, given the way Keil tools are designed.

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