Specifications

Conclusion
 DSP56800 Hardware Interface Techniques 25
4.7 Quadrature Decoder Interface
The DSP56F807EVM board contains a Primary and Secondary Quadrature Encoder/Hall-Effect
interface connected to the DSP’s first and second Quad Encoder input ports. The circuit is designed to
accept +3.0V to +5.0V encoder or Hall-Effect sensor inputs. Input noise filtering is supplied on the
input path for the Quadrature Encoder/Hall-Effect interface, along with additional noise rejection
circuitry inside the DSP. Figure 24 contains the primary encoder interface. The secondary encoder
interface is a duplicate of the primary encoder interface.
4.8 Zero-Crossing Detection
An attached UNI-3 motor drive board contains logic that can send out pulses when the phase voltage
of an attached 3-phase motor drops to zero. The motor drive board circuits generate a 0 to +5.0V DC
pulse via voltage comparators. The resulting pulse signals are sent to a set of jumper blocks shared
with the Encoder/Hall-Effect interface. The jumper blocks allow the selection of Zero-Crossing signals
or Quadrature Encoder/Hall-Effect signals. When in operation, the DSP will only monitor one set of
signals, Encoder/Hall-Effect or Zero-Crossing. Figure 24 contains the Zero-Crossing and
Encoder/Hall circuits.
Figure 24. Zero-Crossing Encoder Interface
5. Conclusion
In this document, we have examined DSP56800 device hardware interfaces, including those
supporting system functions, external memory, and device peripherals. With respect to each of these
categories of interfaces, we have seen that the sophistication of the DSP56800 device translates into
numerous ways in which to interface it to the rest of a system. For example, multiple clocking modes,
versatile memory access aided by software-programmable wait states and memory extension
techniques via external hardware, and the highly configurable, rich peripheral sets of the devices are
easily supported. The results of the high level of integration of memories and peripherals simplify
system design, and reduce system cost.
The hardware designer is encouraged to consult the included list of references.
ZERO_X_A
ZERO_X_B
ZERO_X_C
1
2
3
4
5
6
+5.0V
FILTER
FILTER
FILTER
FILTER
PIN 1: +5.0V
PIN 2: GROUND
PIN 3: PHASE A
PIN 4: PHASE B
PIN 5: INDEX
PIN 6: HOME
1
2
3
4
5
6
7
8
9
JG12
DSP56F807
PHASEA1
PHASEB1
INDEX1
HOME 1
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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