Datasheet

ADSP-21489 EZ-Board Evaluation System Manual 1-13
Using ADSP-21489 EZ-Board
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 “External
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.
Temperature Sensor Interface
Two external pins (THD_P and THD_M) of the processor are connected to an
internal thermal diode. The EZ-Board uses ON Semiconductor’s
ADM1032 digital thermometer and under/over temperature alarm to
monitor the processor’s temperature as well as the thermal diode’s (inside
the ADM1032 device). The thermometer uses the I
2
C bus, DPI pins, and
flag pins of the processor. The following DPI and flag pins are used for
temperature monitoring.
• DPI pin 8 (
DPI_P8) as the serial clock signal (SCK)
• DPI pin 7 (
DPI_P7) as the serial data signal (SDA)
• Flag 0 as the IRQ (not used by default)
• Flag 3 as the thermal limit (not used by default)
The two DPI pins are required: the pins are connected to the temperature
sensing monitor via a switch (
SW3) and can be shut off if the pins are used
on the expansion II interface. The thermal limit flag is connected to