DSP56004SLASHD datasheet(13/82 Pages) FREESCALE

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Signal/Connection Descriptions

Interrupt and Mode Control

MOTOROLA

DSP56004/D, Rev. 3

1-7

INTERRUPT AND MODE CONTROL

The interrupt and mode control signals select the DSP’s operating mode as it comes

out of hardware reset and receives interrupt requests from external sources after

reset.

Table 1-7

Interrupt and Mode Control Signals

Signal Name

Signal

Type

State during

Reset

Signal Description

MODA

IRQA

Input

Input (MODA) Mode Select A—This input signal has three functions:

•

to work with the MODB and MODC signals to select

the DSP’s initial operating mode,

•

to allow an external device to request a DSP

interrupt after internal synchronization, and

•

to turn on the internal clock generator when the DSP

is in the Stop processing state, causing the DSP to

resume processing.

MODA is read and internally latched in the DSP when the

processor exits the Reset state. The logic state present on the

MODA, MODB, and MODC pins selects the initial DSP

operating mode. Several clock cycles after leaving the Reset

state, the MODA signal changes to the external interrupt

request IRQA. The DSP operating mode can be changed by

software after reset.

External Interrupt Request A (IRQA)

—The IRQA input is a

synchronized external interrupt request. It may be

programmed to be level-sensitive or negative-edge-

triggered. When the signal is edge-triggered, triggering

occurs at a voltage level and is not directly related to the fall

time of the interrupt signal. However, as the fall time of the

interrupt signal increases, the probability that noise on IRQA

will generate multiple interrupts also increases.

While the DSP is in the Stop mode, asserting IRQA gates on

the oscillator and, after a clock stabilization delay, enables

clocks to the processor and peripherals. Hardware reset

causes this input to function as MODA.

Freescale Semiconductor, Inc.

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