Motorola DSP56012 Manuel D’Utilisation

MODC/NMI

Input Input

— This 

input has two functions: 

1.

to select the initial chip operating mode, and

2.

after internal synchronization, to allow an 
external device to request a non-maskable DSP 
interrupt. 

MODC is read and internally latched in the DSP when the 
processor exits the Reset state. MODA, MODB, and 
MODC select the initial chip operating mode. Several 
clock cycles (depending on PLL stabilization time) after 
leaving the Reset state, the MODC signal changes to the 
nonmaskable external interrupt request NMI. After reset, 
the chip operating mode can be changed by software. The 
NMI input is an external interrupt request that indicates 
that an external device is requesting service. It may be 
programmed to be level-sensitive or 
negative-edge-sensitive. 

RESET

Input Input

This input is a direct hardware reset on the 

processor. When RESET is asserted low, the DSP is 
initialized and placed in the Reset state. A Schmitt trigger 
input is used for noise immunity. When the RESET signal 
is deasserted, the initial chip operating mode is latched 
from the MODA, MODB, and MODC signals. The 
internal reset signal is deasserted synchronous with the 
internal clocks. In addition, the PINIT pin is sampled and 
written into the PEN bit of the PLL Control Register.

Interrupt and Mode Control (Continued)