Analog Devices ADSP-2181 Interrupt Vector, Source of Interrupt Address Hex, Highest Priority

ADSP-2181/ADSP-2183

Table I. Interrupt Priority & Interrupt Vector Addresses

			Interrupt Vector
Source of Interrupt			Address (Hex)
Reset (or Power-Up with PUCR = 1)			0000	(Highest Priority)
Power Down (Nonmaskable)			002C
IRQ2			0004
IRQL1			0008
IRQL0			000C
SPORT0 Transmit			0010
SPORT0 Receive			0014
IRQE			0018
BDMA Interrupt			001C
SPORT1 Transmit or		IRQ1	0020
SPORT1 Receive or	IRQ0		0024
Timer			0028	(Lowest Priority)

Interrupt routines can either be nested with higher priority in- terrupts taking precedence or processed sequentially. Interrupts can be masked or unmasked with the IMASK register. Indi- vidual interrupt requests are logically ANDed with the bits

in IMASK; the highest priority unmasked interrupt is then selected. The power-down interrupt is nonmaskable.

The ADSP-2181/ADSP-2183 masks all interrupts for one in- struction cycle following the execution of an instruction that modifies the IMASK register. This does not affect serial port autobuffering or DMA transfers.

The interrupt control register, ICNTL, controls interrupt nest- ing and defines the IRQ0, IRQ1, and IRQ2 external interrupts to be either edge- or level-sensitive. The IRQE pin is an external edge sensitive interrupt and can be forced and cleared. The IRQL0 and IRQL1 pins are external level sensitive interrupts.

The IFC register is a write-only register used to force and clear interrupts.

On-chip stacks preserve the processor status and are automati- cally maintained during interrupt handling. The stacks are twelve levels deep to allow interrupt, loop, and subroutine nesting.

The following instructions allow global enable or disable servic- ing of the interrupts (including power down), regardless of the state of IMASK. Disabling the interrupts does not affect serial port autobuffering or DMA.

ENA INTS;

DIS INTS;

When the processor is reset, interrupt servicing is enabled.

LOW POWER OPERATION

The ADSP-2181/ADSP-2183 has three low power modes that significantly reduce the power dissipation when the device oper- ates under standby conditions. These modes are:

•Power Down

•Idle

•Slow Idle

The CLKOUT pin may also be disabled to reduce external power dissipation.

Power Down

The ADSP-2181/ADSP-2183 processor has a low power feature that lets the processor enter a very low power dor- mant state through hardware or software control. Here is a brief list of power-down features. Refer to the ADSP-2100 Family User’s Manual, Chapter 9 “System Interface” for de- tailed information about the power-down feature.

•Quick recovery from power down. The processor begins executing instructions in as few as 100 CLKIN cycles.

•Support for an externally generated TTL or CMOS pro- cessor clock. The external clock can continue running during power down without affecting the lowest power rat- ing and 100 CLKIN cycle recovery.

•Support for crystal operation includes disabling the oscil- lator to save power (the processor automatically waits 4096 CLKIN cycles for the crystal oscillator to start and stabi- lize), and letting the oscillator run to allow 100 CLKIN cycle start up.

•Power down is initiated by either the power-down pin (PWD) or the software power-down force bit.

•Interrupt support allows an unlimited number of instruc- tions to be executed before optionally powering down. The power-down interrupt also can be used as a non- maskable, edge sensitive interrupt.

•Context clear/save control allows the processor to con- tinue where it left off or start with a clean context when leaving the power-down state.

•The RESET pin also can be used to terminate power down.

•Power-down acknowledge pin indicates when the proces- sor has entered power down.

Processor supply current during power down varies with temperature, see Figures 8 and 15.

Idle

When the ADSP-2181/ADSP-2183 is in the Idle Mode, the processor waits indefinitely in a low power state until an interrupt occurs. When an unmasked interrupt occurs, it is serviced; execution then continues with the instruction fol- lowing the IDLE instruction.

Slow Idle

The IDLE instruction is enhanced on the ADSP-2181/ ADSP-2183 to let the processor’s internal clock signal be slowed, further reducing power consumption. The reduced clock frequency, a programmable fraction of the normal clock rate, is specified by a selectable divisor given in the IDLE instruction. The format of the instruction is

IDLE (n);

where n = 16, 32, 64, or 128. This instruction keeps the processor fully functional, but operating at the slower clock rate. While it is in this state, the processor’s other internal clock signals, such as SCLK, CLKOUT, and timer clock, are reduced by the same ratio. The default form of the in- struction, when no clock divisor is given, is the standard IDLE instruction.

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