Description
Reset
Type
Name
Bit/Field
EPSR
ICI / IT status
These bits, along with bits 15:10, contain the Interruptible-Continuable
Instruction (
ICI
) field for an interrupted load multiple or store multiple
instruction or the execution state bits of the
IT
instruction.
When
EPSR
holds the
ICI
execution state, bits 26:25 are zero.
The If-Then block contains up to four instructions following an
IT
instruction. Each instruction in the block is conditional. The conditions
for the instructions are either all the same, or some can be the inverse
of others. See the Cortex™-M4 instruction set chapter in the
ARM®
Cortex™-M4 Devices Generic User Guide (literature number
)
for more information.
The value of this field is only meaningful when accessing
PSR
or
EPSR
.
Note that these
EPSR
bits cannot be accessed using
MRS
and
MSR
instructions but the definitions are provided to allow the stacked (E)PSR
value to be decoded within an exception handler.
0x0
RO
ICI / IT
26:25
EPSR
Thumb State
This bit indicates the Thumb state and should always be set.
The following can clear the
THUMB
bit:
■
The
BLX
,
BX
and
POP{PC}
instructions
■
Restoration from the stacked
xPSR
value on an exception return
■
Bit 0 of the vector value on an exception entry or reset
Attempting to execute instructions when this bit is clear results in a fault
or lockup. See “Lockup” on page 125 for more information.
The value of this bit is only meaningful when accessing
PSR
or
EPSR
.
1
RO
THUMB
24
Software should not rely on the value of a reserved bit. To provide
compatibility with future products, the value of a reserved bit should be
preserved across a read-modify-write operation.
0x00
RO
reserved
23:20
Greater Than or Equal Flags
See the description of the
SEL
instruction in the Cortex™-M4 instruction
set chapter in the
ARM® Cortex™-M4 Devices Generic User Guide
(literature number
)
for more information.
The value of this field is only meaningful when accessing
PSR
or
APSR
.
0x0
RW
GE
19:16
June 18, 2014
94
Texas Instruments-Production Data
The Cortex-M4F Processor