ADSP-BF535 Blackfin Processor Hardware Reference
3-7
Operating Modes and States
Supervisor mode has full, unrestricted access to all processor system
resources, including all emulation resources unless a CPLB has been con-
figured and enabled, as described in
“Memory Management Unit” on
page 6-56
. Only Supervisor mode can use the register alias
USP
, which
locates the User Stack Pointer in memory.
Normal processing begins in Supervisor mode from the Reset state. Deas-
serting the
RESET
signal switches the processor from the Reset state to
Supervisor mode where it remains until an emulation event or Return
instruction occurs to change the mode. Before the return instruction is
issued, the
RETI
register must be loaded with a valid return address.
Non-OS Environments
For non-OS environments, application code should remain in Supervisor
mode so that it can access all core and system resources. When
RESET
is
deasserted, the processor initiates operation by servicing the reset event.
Emulation is the only event that can preempt this activity. Lower priority
events cannot be processed.
One method to keep the processor in Supervisor mode and still allow
lower priority events to be processed can be implemented by setting up
and forcing the lowest priority interrupt (
IVG15
). Events and interrupts are
described further in
“Events and Sequencing” on page 4-17
. Once the low
priority interrupt has been forced using the
RAISE 15
instruction,
RETI
can be loaded with a return address that points to user code that can exe-
cute until
IVG15
is issued. Once
RETI
has been loaded, the
RTI
instruction
can be issued to return from the reset event.
The interrupt handler for
IVG15
can be set to jump to the application code
starting address. An additional
RTI
is not required. As a result, the proces-
sor remains in Supervisor mode because
IPEND[15]
remains set. At this
point, the processor is servicing the lowest priority interrupt. This ensures
that higher priority interrupts can be processed.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...