SN52020
2-Channel Speech Controller
5.10. Watch Dog
The WDT is cascade after system timer. When user reset system timer will issue a
clear signal to WDT also. It would issue a reset signal to chip if user doesn’t reset any
system timer before it reach terminate count (1 Second) when chip is in active mode.
5.11. I/O Ports
P3 is a 4-bit I/O port. Any bit of P3 can be programmed to be input or output
individually. Any valid data transition (H L or L H) of P3 can reactivate the chip
when it is in power-down stage.
Port Data
Port Status
PAD
Weak
Pull Low enable
To Internal Data Bus
Read Control
I/O Port Configuration (P30~P33)
Note: All weak N-MOS’s can serve as pull-low resistors.
5.12. Pull-Low Resister Control
This function provides user to control Pull-Low register of all I/O ports that can be
disabled by user command. With the help of this function, input floating and input pull
low is supported.
Ver: 1.0
7
March 2,2005