Table 2-7 Interrupt And Mode Control Signals - Motorola DSP56009 User Manual

Signal Descriptions
Interrupt and Mode Control
2.6 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 2-7 Interrupt and Mode Control Signals

Signal Signal
Name Type
MODA Input
IRQA
2-10
State during
Reset
Input Mode Select A—This input signal has three
(MODA) functions:
• to work with the MODB and MODC signals
• to allow an external device to request a DSP
• to turn on the internal clock generator when
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.
DSP56009 User's Manual
Signal Description
to select the DSP's initial operating mode,
interrupt after internal synchronization, and
the DSP in the Stop processing state, causing
the DSP to resume processing.
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