Freescale Semiconductor StarCore SC140 - Manual (Page 108)

3-8 SC140 DSP Core Reference Manual
Core Control Registers
Table 3-2 describes the EMR fields.
Table 3-2. EMR Description
Name Description Settings
R
Bits 31–24 Reserved
GP6–GP0
Bits 23–17 General Purpose Flags — Use of these bits is
dependent on the state of external pins. Their
function is specific to the SoC.
BEM
Bit 16 Big Endian Memory Bit — Indicates big endian
or little endian memory configuration. See
Section 2.4.1, “SC140 Endian Support,” for more
information.
This bit is dependent on the state of an external
pin. This pin is sampled at core reset.
0 = Little endian configuration
1 = Big endian configuration
R
Bits 15–4 Reserved
NMID
Bit 3 Non-maskable Interrupt (NMI) Disable Bit —
Set when an NMI service routine enters execution
such as when the NMI vector is fetched. While this
bit is set, no pending NMI requests are serviced.
The bit is cleared by an RTE instruction, or by
writing back 1 to it as explained in
Section 3.1.2.1,
“Clearing EMR Bits.”
The NMI bit cannot be set by the user. It is cleared
at reset.
0 = No NMI service executing
1 = NMI service executing
DOVF
Bit 2 DALU Overflow Bit — Indicates that an overflow
from 40 bits occurred during a DALU operation, or
that arithmetic saturation occurred in arithmetic
saturation mode (overflow from 32 bits).
Whenever there is an overflow, an exception is
generated if the OVE bit is set in the SR. Until the
bit is cleared, no new exceptions are generated.
The DOVF bit is a sticky bit. The bit is set if the
appropriate exception occurred. It can only be
cleared by writing back 1 to it as explained in
Section 3.1.2.1, “Clearing EMR Bits.”
The DOVF bit cannot be set by the user, only by
the hardware. It is cleared at reset.
If the OVE bit is set, the clearing operation should
only be performed during the overflow exception
service routine.
Due to pipeline effects, the overflow exception is
not serviced immediately after the instruction that
caused the overflow condition.
0 = No overflow or arithmetic saturation occurred
1 = Overflow or arithmetic saturation occurred