ADSP-21479 EZ-Board Evaluation System Manual
1-17
Using The ADSP-21479 EZ-Board
The audio codec is set up to use DPI pin 4 as the SPI chip select. For more
information, refer to
“Audio Interface” on page 1-20
.
Watch Dog Timer Interface
The ADSP-21479 processor includes a 32-bit watch dog timer (WDT)
that can be used to implement a software watch dog function. A software
watch dog can improve system reliability by forcing the processor to a
known state through generation of a system reset if the timer expires
before being reloaded by software. Software initializes the count value of
the timer and then enables the timer.
The watch dog timer resets both the core and internal peripherals. After
an external reset, the WDT must be disabled by default. Software must be
able to determine if the watch dog has been the source of the hardware
reset by interrogating a status bit in the watch dog timer control register.
Be default, the watch timer interface is turned off. In order to use the fea-
ture, a user needs to turn switch
SW13
position 8
ON
.
SW13
connects the
watch dog reset out pin to the ADM708 system reset circuit. See
Port Enable Switch (SW13)” on page 2-12
. Special attention must be paid
to this function because it can cause the processor and EZ-Board to
remain in a permanent reset.
Example programs are included in the EZ-Board installation directory to
demonstrate watch dog timer functionality.
Real-Time Clock Interface
The real-time clock (RTC) of the ADSP-21479 processor provides a
robust set of digital watch features, including current time, stopwatch, and
alarm. The RTC is clocked by a 32.768 kHz crystal external to the proces-
sor. The RTC peripheral has dedicated power supply pins so that it can
remain powered up and clocked even when the rest of the processor is in a
