Data Sheet
June 2001
DSP16410B Digital Signal Processor
30
Agere Systems—Proprietary
Use pursuant to Company instructions
Agere Systems Inc.
4 Hardware Architecture
(continued)
4.4 Interrupts and Traps
(continued)
4.4.3 Clearing Core Interrupt Requests
Internal hardware interrupt signals are pulses that the
core latches into its
ins
register (see
Section 4.4.7 on
page 32
). Therefore, the user software need not clear
the interrupt request. However, in the case of the PIU
host interrupt, PHINT, the user software must clear the
HINT field (
PCON
[4]) to allow the host to request a
subsequent interrupt. See
Section 4.15.7 on page 150
for details.
4.4.4 Host Interrupt Output
The DSP16410B provides an interrupt output pin,
PINT, that can interrupt a host processor connected to
the PIU. A core can assert this pin by setting the PINT
field (
PCON
[3]). The host must clear the PINT field to
allow a core to request a subsequent interrupt. See
Section 4.15.7 on page 150
for details.
4.4.5 Globally Enabling and Disabling Hardware
Interrupts
A device reset globally disables interrupts, i.e., the core
does not service interrupts by default after reset. The
application must execute an
ei
instruction to globally
enable interrupts, i.e., to cause the core to service
interrupts that are individually enabled.
Section 4.4.6
on page 31
describes individually enabling and dis-
abling interrupts. Executing the
di
instruction globally
disables interrupts.
The core automatically globally disables interrupts if it
begins servicing an interrupt. Therefore, an interrupt
service routine (ISR) cannot be interrupted unless the
programmer places an
ei
instruction within the ISR. In
other words, interrupt nesting is disabled by
default. When the
ireturn
instruction that the program-
mer must place at the end of the ISR is executed, the
core automatically globally re-enables interrupts.
Therefore, the programmer does not need to explicitly
re-enable interrupts by executing an
ei
instruction
before exiting the ISR. To nest interrupts, the program-
mer must place an
ei
and a
di
instruction within an
ISR. See
Section 4.4.11 on page 35
for details on
nesting.
The one-bit IEN field (
psw1
[14]—see
Table 10 on
page 35
) is cleared if hardware interrupts are globally
disabled. The IEN field is set if interrupts are globally
enabled.
Table 6
summarizes global disabling and enabling of
hardware interrupts.
Table 6. Global Disabling and Enabling of Hardware Interrupts
Condition
Hardware interrupts
globally
disabled
Caused by
Indicated by
IEN (
psw1
[14]) = 0
Effect
Device reset
Execution of a
di
instruction
The core begins to service an interrupt
Execution of an
ei
instruction
Core does not service
interrupts.
Hardware interrupts
globally
enabled
Execution of an
ireturn
instruction
IEN (
psw1
[14]) = 1
Core services individually
enabled interrupts.
With the exception of device reset, CORE0 and CORE1 are independent with respect to global disabling and enabling of hardware interrupts.