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

Instruction Details
A8.6.223 SXTB
Signed Extend Byte extracts an 8-bit value from a register, sign-extends it to 32 bits, and writes the result to
the destination register. You can specify a rotation by 0, 8, 16, or 24 bits before extracting the 8-bit value.
Encoding T1 ARMv6*, ARMv7
SXTB ,
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 0 1 1 0 0 1 0 0 1 Rm Rd
d = UInt(Rd); m = UInt(Rm); rotation = 0;
Encoding T2 ARMv6T2, ARMv7
SXTB.W ,{,}
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
1 1 1 1 1 0 1 0 0 1 0 0 1 1 1 1 1 1 1 1 Rd 1 (0) rotate Rm
d = UInt(Rd); m = UInt(Rm); rotation = UInt(rotate:’000’);
if BadReg(d) || BadReg(m) then UNPREDICTABLE;
Encoding A1 ARMv6*, ARMv7
SXTB ,{,}
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
cond 0 1 1 0 1 0 1 0 1 1 1 1 Rd rotate (0)(0) 0 1 1 1 Rm
d = UInt(Rd); m = UInt(Rm); rotation = UInt(rotate:’000’);
if d == 15 || m == 15 then UNPREDICTABLE;
A8-440 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B