Power, Ground, And Clock (28 Pins) - Motorola DSP56156 Manual

chip operating mode is latched from the MODA and MODB pins. The internal
reset signal should be deasserted synchronous with the internal clocks.
2.5

POWER, GROUND, AND CLOCK (28 PINS)

VCC (8) (Power) - power pins.
VSS (14) (Ground) - ground pins.
VDDS (Synthesizer Power) - This pin supplies a quiet power source to the PLL to pro-
vide greater frequency stability.
GNDS (Synthesizer Ground) - This pin supplies a quiet ground source to the PLL to
provide greater frequency stability.
VDDA (Power Supply input) - This pin is the positive analog supply input. It should
be connected to VCC when the codec is not used.
(Analog Ground) - This pin is the analog ground return. It should be connected
VSSA
to VSS when the codec is not used.
(External Clock/Crystal Input) - This input should be connected to an external
EXTAL
clock or to an external oscillator. After being squared, the input frequency can
be used as the DSP core internal clock. In that case, it is divided by two to pro-
duce a four phase instruction cycle clock, the minimum instruction time being
two input clock periods.This input frequency is also used, after division, as input
clock for the on-chip codec and the on-chip phase locked loop (PLL).
CLKO (Clock Output) - This pin outputs a buffered clock signal. By programming two
bits (CS1-CS0) inside the PLL Control Register (PLCR), the user can select be-
tween outputting a squared version of the signal applied to EXTAL, a squared
version of the signal applied to EXTAL divided by 2, and a delayed version of
the DSP core master clock. The clock frequency on this pin can be disabled by
setting the Clockout Disable bit (CD; bit 7) of the Operating Mode Register
(OMR). In this case, the pin can be left floating.
(External Filter Capacitor) - This pin is used to add an external capacitor to
SXFC
the PLL filter circuit. A low leakage capacitor should be connected between
SXFC and VDDS; it should be located very close to those pins.
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POWER, GROUND, AND CLOCK (28 PINS)

DSP56156 PIN DESCRIPTIONS MOTOROLA