Protected Memory; Entering User Mode; Example Code To Enter User Mode Upon Reset; Return Instructions That Invoke User Mode - Analog Devices ADSP-BF53x Blackfin Reference

Protected Memory

Additional memory locations can be protected from User mode access. A
Cacheability Protection Lookaside Buffer (CPLB) entry can be created
and enabled. See
information.

Entering User Mode

When coming out of reset, the processor is in Supervisor mode because it
is servicing a reset event. To enter User mode from the Reset state, two
steps must be performed. First, a return address must be loaded into the
register. Second, an
RETI
shows how to enter User mode upon reset.

Example Code to Enter User Mode Upon Reset

Listing 3-1 provides code for entering User mode from reset.
Listing 3-1. Entering User Mode from Reset
P1.L = START ;
P1.H = START ;
RETI = P1 ;
RTI ; /* Return from Reset Event */
START : /* Place user code here */

Return Instructions That Invoke User Mode

Table 3-4 provides a summary of return instructions that can be used to
invoke User mode from various processor event service routines. When
these instructions are used in service routines, the value of the return
address must be first stored in the appropriate event
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
"Memory Management Unit" on page 6-45
must be issued. The following example code
RTI
/* Point to start of user code */
Operating Modes and States
RETx
for further
register. In the
3-5