Specifications

Standard Initialization Sequence for Hercules Microcontrollers

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The Cortex-R4F CPU can operate in one of several modes:

• User mode (USR) is the usual mode for the execution of ARM or Thumb programs. It is used for

executing most application programs. Many control registers on the Hercules microcontroller are not

writable in user mode.

cps #16

ldr sp, user

• Fast interrupt mode (FIQ) is entered upon taking a fast interrupt.

cps #17

ldr sp, fiq

• Interrupt mode (IRQ) is entered on taking a normal interrupt.

cps #18

ldr sp, irq

• Abort mode (ABT) is entered after a data or instruction abort.

cps #23

ldr sp, abort

• Undefined mode (UND) is entered when an undefined instruction exception occurs.

cps #27

ldr sp, undef

• System mode (SYS) is a privileged mode for the operating system.

cps #31

ldr sp, sys

• Supervisor mode (SVC) is a protected mode for the operating system and is entered upon taking a

Supervisor Call (SVC). This is also the default mode of the CPU after a CPU reset.

cps #19

ldr sp, svc

The application can initialize the stack pointers in the above sequence. This will leave the CPU in the

Supervisor (SVC) mode once the stack pointers are initialized.

2.21 Vectored Interrupt Manager Configuration

The Vectored Interrupt Manager (VIM) module on the Hercules microcontrollers supports flexible mapping

of interrupt request channels and the interrupt generating sources. The default mapping between the

channel number and the interrupting module is defined in the device datasheet. The interrupt channel

number also defines the inherent priority between the channels, with the lower numbered channel having

the higher priority. That is, the priority decreases in the following order: channel 0 → channel 1 → channel

2 → … channel 95.

For this application report, assume that the application prefers to keep the default priority order between

the channels. For details on the control registers for changing the mapping between interrupt channels

and sources, see the specific part's technical reference manual.

Initialization of Hercules™ ARM

Cortex™-R4F Microcontrollers SPNA106– September 2011

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