EALLOW
6-90
EALLOW Enable Write Access to Protected Space
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
EALLOW 0111 0110 0010 0010 X − 4
Operands None
Description Enable access to emulation space and other protected registers.
This instruction sets the EALLOW bit in status register ST1. When this bit is
set, the C28x CPU allows write access to the memory-mapped registers as
well as other protected registers. See the data sheet for your particular
device to determine which registers the EALLOW bit protects.
To again protect against writes to the registers, use the EDIS instruction.
EALLOW only controls write access; reads are allowed even if EALLOW
has not been executed.
On an interrupt or trap, the current state of the EALLOW bit is saved off onto
the stack within ST1 and the EALLOW bit is autocratically cleared.
Therefore, at the start of an interrupt service routine access to the protected
registers is disabled. The IRET instruction will restore the current state of
the EALLOW bit saved on the stack.
The EALLOW bit is overridden via the JTAG port, allowing full control of
register accesses during debug from Code Composer Studio.
Flags and
Modes
EALLOW
The EALLOW flag is set.
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example
; Enable access to RegA and RegB which are EALLOW protected:
EALLOW ; Enable access to selected registers
AND @RegA,#0x4000 ; RegA = RegA AND 0x0400
MOV @RegB,#0 ; RegB = 0
EDIS ; Disable access to selected registers
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