Motorola DSP56009 User Manual page 49

Table 2-7 Interrupt and Mode Control Signals (Continued)
Signal Signal
Name Type
MODB Input
IRQB
MOTOROLA
State during
Reset
Input Mode Select B— This input signal has two functions:
(MODB)
• to work with the MODA and MODC signals
• to allow an external device to request a DSP
MODB 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 MODB signal
changes to the external interrupt request IRQB. The
DSP operating mode can be changed by software
after reset.
External Interrupt Request B (IRQB)—The IRQB
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 IRQB will generate multiple interrupts also
increases. Hardware reset causes this input to
function as MODB.
DSP56009 User's Manual
Interrupt and Mode Control
Signal Description
to select the DSP's initial operating mode, and
interrupt after internal synchronization.
Signal Descriptions
2-11