RCR              Rotate through Carry Right          Flags: O D I T S Z A P C
*               *
RCR destination,count

      Destination        CF   

RCR shifts the word or byte at the destination to the right by the
number of bit positions specified in the second operand, COUNT. A bit
shifted out of the right (low-order) end of the destination enters the
carry flag, and the displaced carry flag rotates around to enter the
vacated left-most bit position of the destination. This "bit rotation"
continues the number of times specified in COUNT. (Another way of
looking at this is to consider the carry flag as the lowest order bit
of the word being rotated.)

If COUNT is not equal to 1, the Overflow flag is undefined. If COUNT
is equal to 1, the Overflow Flag is set to the XOR of the top 2 bits
of the result.

Operands                  Clocks   Transfers  Bytes   Example
register, 1                 2          -        1     RCR CX,1
register, CL            8 + 4/bit      -        2     RCR DL,CL
memory, 1              15(23) + EA     2       2-4    RCR DIVIDE_BY_2,1
memory, CL           20(28)+EA+4/bit   2       2-4    RCR AROUND_MOVE,CL

Notes:         COUNT is normally taken as the value in CL. If,
however, you wish to rotate only one position,
replace the second operand, CL, with the value 1, as
shown in the first example above.

The 80286 and 80386 microprocessors limit the COUNT
value to 31.  If COUNT is greater than 31, these
microprocessors use COUNT MOD 32 to produce a new
COUNT between 0 and 31.  This upper bound exists to
limit the amount of time an interrupt response will
be delayed waiting for the instruction to complete.

Multiple RCRs that use 1 as the COUNT may be faster
and require less memory than a single RCR that uses

The overflow flag is undefined if the rotate count
is greater than 1.

See also: ROR
See also: RCL
See also: ROL
See also: SAR
See also: SHR
See also: SHL
See also: SAL
See also: EA
See also: Flags

RCR Rotate through Carry Right