SNC521

One Channel Direct Drive Speech Controller

Ver: 1.3

August 26, 2003

4

5.6. I/O Ports

P2 and P3 are two 4-bit I/O ports. Any bit of P2 and P3 can be programmed as

either input or output port individually. Any valid data transition (H

L or L H) of

P2 and P3 can reactivate the chip when the chip is in power-down stage.

I/O Port Configuration (P20~P23, P30~P33)

Note: Weak N-MOS can serve as pull-low resistor.

5.7. DAC & PWM

SNC521 is an advanced chip to be designed having two optimal methods to play

out the voices. One is DAC and the other is PWM. Upon user’s applications, user

can select either DAC or PWM in his design. Please be aware that only one

method can be activated at a time.

DAC: A 7-bit current type digital-to-analog converter is built-in SNC521. The

relationship between input digital data and output analog current signal is listed

in the following table. Also, the recommended application circuit is illustrated as

follows.

Port Data

Port Status

To Internal Data Bus

Read Control

PAD

Weak