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ARM INSTRUCTION SET S3C2440A RISC MICROPROCESSOR
3-14
Rotate right (ROR) operations reuse the bits which "overshoot" in a logical shift right operation by reintroducing
them at the high end of the result, in place of the zeros used to fill the high end in logical right operations. For
example, ROR #5 is shown in Figure 3-9.
31
Contents of Rm
Value of Operand 2
0
carry out
45
Figure 3-9. Rotate Right
The form of the shift field which might be expected to give ROR #0 is used to encode a special function of the
barrel shifter, rotate right extended (RRX). This is a rotate right by one bit position of the 33 bit quantity formed by
appending the CPSR C flag to the most significant end of the contents of Rm as shown in Figure 3-10.
31
Contents of Rm
Value of Operand 2
01
carry out
C
in
Figure 3-10. Rotate Right Extended