48
The 68000's Instruction Set
Description: Rotate the bits of the operand in the direction indicated. The
extend bit of the CCR is included in the rotation. A rotate
operation is circular in the sense that the bit shifted out at one
end is shifted into the other end. That is, no bit is lost or destroyed
by a rotate operation. Since the X-bit is included in the rotate, the
rotation is performed over 9 bits (.B), 17 bits (.W), or 33 bits (.L).
The bit shifted out is also copied into the C-bit of the CCR as well
as the X-bit. The shift count may be specified in one of three
ways: the count may be a literal, the contents of a data register,
or the value 1. An immediate count permits a shift of 1 to 8
places. If the count is in a register, the value is modulo 64 and the
range is from 0 to 63. If no count is specified, the word at the
specified effective address is rotated by one place (i.e., ROXL <ea>).
Condition codes: X N Z V C
* * * 0 *
The X- and the C-bit are set to the last bit rotated out of the
operand. If the rotate count is zero, the X-bit is unaffected and
the C-bit is set to the X-bit.
Destination operand addressing modes
RTE Return from exception
Operation: IF [S] = 1 THEN
[SR]
← [M([SP])]; [SP] ← [SP] + 2
[PC]
← [M([SP])]; [SP] ← [SP] + 4
ELSE TRAP
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