Freescale Semiconductor SC140 specifications Describes the EMR fields, EMR Description

Core Control Registers

Table 3-2 describes the EMR fields.

	Table 3-2. EMR Description
Name	Description	Settings
R	Reserved
Bits 31–24
GP6–GP0	General Purpose Flags — Use of these bits is
Bits 23–17	dependent on the state of external pins. Their
	function is specific to the SoC.
BEM	Big Endian Memory Bit — Indicates big endian	0 = Little endian configuration
Bit 16	or little endian memory configuration. See	1 = Big endian configuration
	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.
R	Reserved
Bits 15–4
NMID	Non-maskable Interrupt (NMI) Disable Bit —	0 = No NMI service executing
Bit 3	Set when an NMI service routine enters execution	1 = NMI service executing
	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.
DOVF	DALU Overflow Bit — Indicates that an overflow	0 = No overflow or arithmetic saturation occurred
Bit 2	from 40 bits occurred during a DALU operation, or	1 = Overflow or arithmetic saturation occurred
	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.

3-8 SC140 DSP Core Reference Manual