Motorola DSP56009 User Manual page 50

Signal Descriptions
Interrupt and Mode Control
Table 2-7 Interrupt and Mode Control Signals (Continued)
Signal Signal
Name Type
MODC/ Input,
NMI edge-
triggered
2-12
State during
Reset
Input Mode Select C—This input signal has two functions:
(MODC)
• to work with the MODA and MODB signals
• to allow an external device to request a DSP
MODC 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 MODC signal
changes to the Non-Maskable Interrupt request,
NMI. The DSP operating mode can be changed by
software after reset.
Non-Maskable Interrupt Request—The NMI input
is a negative-edge-triggered external interrupt
request. This is a level 3 interrupt that can not be
masked out. 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 NMI
will generate multiple interrupts also increases.
Hardware reset causes this input to function as
MODC.
DSP56009 User's Manual
Signal Description
to select the DSP's initial operating mode, and
interrupt after internal synchronization.
MOTOROLA