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INSTRUCTION SET
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. The form of the shift field which might be expected to give ROR #0 is
31
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
C
in
3-14
Contents of Rm
Value of Operand 2
Figure 3-9. Rotate Right
Contents of Rm
Value of Operand 2
Figure 3-10. Rotate Right Extended
S3C2500B
5
4
0
carry out
1
0
carry out
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