Cypress Semiconductor CY7C68013A Uživatelský manuál stáhnout pdf (Strana 2)

easily available ad we would save time in acquisition of a 100 pin cotroller. The FIFOs

available as free samples are unidirectional and this would require multiplexing of the

data lines between the DSP and the controller for data flow in each direction. The

additional overhead would reduce the throughput. This problem can be dealt with using

the internal memory of the DSP.

Figure 1: Block Diagram

3. Design of circuit

3.1 Power supply

The USB port supplies power at 5V. Voltage rating for CY7C68013A chip is 3.3V.

Hence to convert from 5V to 3.3V TPS7333 chip is used. Power supply from the USB

port can supply a maximum of 500mA as and when demanded by the devices connected

to it. Since the maximum current required by our circuit is of the order of 450- 500 mA.

Therefore a provision has been made either to supply power to full circuit by the USB

port or power from USB port only to drive Cypress circuitry and an external power

supply to drive the Digital Signal Processor circuitry including the CPLD chip. A jumper

has been provided to access both the options. In all cases the USB port should be used to

power the controller as the USB peripheral should be powered on plugging the device.

The external Power supply includes a diode bridge in the initial stage to rectify the a.c

signal coming from the transformed-mains and is filtered by the capacitor. This is then

fed to a voltage regulator (7805 LM340H-05 ) to get a stabilized voltage of rating 5 volts.

Since the DSP chip TMS320VC33 requires the voltage supply (V

) of 3.3V and 1.8V, a

circuit to convert 5V to 3.3V and 1.8V was achieved using the TPS768D318 chip and the

associated circuit.

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Cypress Semiconductor CY7C68013A Uživatelský manuál Strana 2