Interrupt Handlers
8-19
DSP Private Peripherals
8.4.2.1
Interrupt Sequence
1) One or several incoming interrupts go down, setting the corresponding
ITR bits.
2) At this time, two possibilities exist:
J
If there is only one active incoming interrupt and FIQ is not already
active, the interrupt controller sends an FIQ.
J
When several incoming interrupts are active, the interrupt controller
must determine which is the new interrupt to be serviced. It does so by
comparing the priority level of an interrupt with the one held in a dedi-
cated register N_FIQ and stores the interrupt with the highest priority
in the dedicated register N_FIQ. It performs this comparison until all
the active interrupts have been processed. If FIQ is not already active,
the interrupt controller sends an FIQ.
3) When an FIQ is sent, the source interrupt encoded register (SIR_FIQ) is
updated (indicating the interrupt contained in N_FIQ) and the priority
resolver is reset (and restarted if necessary).
4) To determine which incoming interrupt has requested a DSP action, the
source interrupt encoded register (SIR_FIQ) must be read. The register
contains an encoded number that tells which interrupt lines are being
serviced. After that, it runs the corresponding subroutine.
5) To finish the interrupt sequence, DSP software must first clear the interrupt
bit in the interrupt input register (ITR) that is being serviced. This is done
by writing a 0 to the corresponding bit in the interrupt input register (ITR)
directly or by reading the source interrupt encoded register (SIR_FIQ). For
a level-sensitive interrupt, the level must also be removed for the next
interrupt to occur. Then set a dedicated bit (NEW_FIQ_AGR bit of the
control register) in order to reset the FIQ output and the source encoded
register (SIR_FIQ), thus allowing a new FIQ generation.
8.4.2.2
DSP Accessible Registers
DSP start word address (hex): 0x004800
Bus width: 16 bits
DSP address of a register = Start a offset TIPB address
Table 8–22 lists the interrupt handler level 2 registers. Table 8–23 through
Table 8–29 describe the register bits.