Sxta.x, Sign-extension (agu), Description – Freescale Semiconductor StarCore SC140 User Manual
Page 716: Example 1, Example 2, Operation assembler syntax
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SC140 DSP Core Reference Manual
SXTA.x
SXTA.x
Sign-Extension (AGU)
SXTA.x
Description
These operations sign-extend an AGU register (address or offset register, program counter, or stack
pointer). The sign bit (bit 7 in a byte or bit 15 in a word) is copied to the upper bits in a 32-bit AGU
register.
Status and Conditions that Affect Instruction
Status and Conditions Changed by Instruction
None.
Example 1
sxta.b r3,r1
Example 2
sxta.w r3
Operation
Assembler Syntax
rx[7:0]
→ Rx[7:0]; rx[7] → Rx[31:8]
SXTA.B rx,Rx
Rx[15]
→ Rx[31:16]
SXTA.W Rx
SXTA.B rx,Rx
Sign-extends a byte from a source AGU register (rx[7:0]) into a destination AGU register (Rx).
SXTA.W Rx
Sign-extends a word from a source AGU register (Rx[15:0]) into a destination AGU register (Rx).
Register Address
Bit Name
Description
SR[18]
EXP
Determines which stack pointer is used when the stack pointer is an
operand. Otherwise, the instruction is not affected by SR.
Register/Memory Address
Before
After
R3
$0000 2086
R1
$FFFF FF86
Register/Memory Address
Before
After
R3
$03BC 8A56
$FFFF 8A56