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9
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ADSP-2195
September 2001
priority level of 11 are aliased to the lowest priority bit
position (15) in these registers and share vector address
0x00 01E0.
Interrupt routines can either be nested with higher priority
interrupts taking precedence or processed sequentially.
Interrupts can be masked or unmasked with the IMASK
register. Individual interrupt requests are logically ANDed
with the bits in IMASK; the highest priority unmasked
interrupt is then selected. The emulation, power-down, and
reset interrupts are nonmaskable with the IMASK register,
but software can use the DIS INT instruction to mask the
power-down interrupt.
The Interrupt Control (ICNTL) register controls interrupt
nesting and enables or disables interrupts globally. The gen-
eral-purpose Programmable Flag (PFx) pins can be
configured as outputs, can implement software interrupts,
and (as inputs) can implement hardware interrupts. Pro-
grammable Flag pin interrupts can be configured for
level-sensitive, single edge-sensitive, or dual edge-
sensitive operation.
The IRPTL register is used to force and clear interrupts.
On-chip stacks preserve the processor status and are auto-
matically maintained during interrupt handling. To support
interrupt, loop, and subroutine nesting, the PC stack is
33 levels deep, the loop stack is eight levels deep, and the
status stack is 16 levels deep. To prevent stack overflow, the
PC stack can generate a stack-level interrupt if the PC stack
falls below three locations full or rises above 28
locations full.
The following instructions globally enable or disable
interrupt servicing, regardless of the state of IMASK.
ENA INT;
DIS INT;
At reset, interrupt servicing is disabled.
For quick servicing of interrupts, a secondary set of DAG
and computational registers exist. Switching between the
primary and secondary registers lets programs quickly
service interrupts, while preserving the DSP’s state.
DMA Controller
The ADSP-2195 has a DMA controller that supports
automated data transfers with minimal overhead for the
DSP core. Cycle stealing DMA transfers can occur between
the ADSP-2195’s internal memory and any of its
DMA-capable peripherals. Additionally, DMA transfers
can be accomplished between any of the DMA-capable
peripherals and external devices connected to the external
memory interface. DMA-capable peripherals include the
Host port, SPORTs, SPI ports, and UART. Each individual
DMA-capable peripheral has a dedicated DMA channel. To
describe each DMA sequence, the DMA controller uses a
Table 2. Peripheral Interrupts and Priority at Reset
Interrupt
ID
Reset
Priority
Slave DMA/Host Port Interface
0
0
SPORT0 Receive
1
1
SPORT0 Transmit
2
2
SPORT1 Receive
3
3
SPORT1 Transmit
4
4
SPORT2 Receive/SPI0
5
5
SPORT2 Transmit/SPI1
6
6
UART Receive
7
7
UART Transmit
8
8
Timer A
9
9
Timer B
10
10
Timer C
11
11
Programmable Flag 0 (any PFx)
12
11
Programmable Flag 1 (any PFx)
13
11
Memory DMA port
14
11
Table 3. Interrupt Control (ICNTL) Register Bits
Bit
Description
0–3
Reserved
4
Interrupt Nesting Enable
5
Global Interrupt Enable
6
Reserved
7
MAC-Biased Rounding Enable
8–9
Reserved
10
PC Stack Interrupt Enable
11
Loop Stack Interrupt Enable
12–15
Reserved