ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

A5.2.4 Modified immediate constants in ARM instructions
ARM Instruction Set Encoding
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Table A5-6 shows the range of modified immediate constants available in ARM data-processing
instructions, and how they are encoded in the a, b, c, d, e, f, g, h, and rotation fields in the instruction.
Note
rotation a b c d e f g h
Table A5-6 Encoding of modified immediates in ARM processing instructions
rotation a
0000 00000000 00000000 00000000 abcdefgh
0001 gh000000 00000000 00000000 00abcdef
0010 efgh0000 00000000 00000000 0000abcd
0011 cdefgh00 00000000 00000000 000000ab
0100 abcdefgh 00000000 00000000 00000000
. .
. .
. .
8-bit values shifted to other even-numbered positions
1001 00000000 00abcdef gh000000 00000000
. .
. .
. .
8-bit values shifted to other even-numbered positions
1110 00000000 00000000 0000abcd efgh0000
1111 00000000 00000000 000000ab cdefgh00
a. In this table, the immediate constant value is shown in binary form, to relate
abcdefgh to the encoding diagram. In assembly syntax, the immediate value
is specified in the usual way (a decimal number by default).
The range of values available in ARM modified immediate constants is slightly different from the range of
values available in 32-bit Thumb instructions. See Modified immediate constants in Thumb instructions on
page A6-17.
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