w681308 Winbond Electronics Corp America, w681308 Datasheet - Page 26

• Manufacturer Part Number: w681308
• Description: Usb Audio Controller
• Manufacturer: Winbond Electronics Corp America

The main use of the Watchdog timer is as a system monitor. This is important in real-time control applications. In case of
some power glitches or electro-magnetic interference, the processor may begin to execute errant code. If this is left
unchecked the entire system may crash. Using the watchdog timer interrupt during software development will allow the user
to select ideal watchdog reset locations. The code is first written without the watchdog interrupt or reset. Then the watchdog
interrupt is enabled to identify code locations where interrupt occurs. The user can now insert instructions to reset the
watchdog timer which will allow the code to run without any watchdog timer interrupts. Now the watchdog timer reset is
enabled and the watchdog interrupt may be disabled. If any errant code is executed now, then the reset watchdog timer
instructions will not be executed at the required instants and watchdog reset will occur.
The Watchdog timer will be disabled by a power-on/fail reset. The Watchdog timer reset does not disable the watchdog timer,
but will restart it.
NOTE: In general, software should restart the timer to put it into a known state.
Control Bit
WDCON
External
Reset
WTRF
WD1
D8H
WDIF
POR
0
0
1
1
Power-on Reset Flag
WD0
Bit 7
Watchdog Timer
Watchdog Timer
0
1
0
1
0
-
Interrupt Flag
Reset Flag
Name
POR
Bit 6
Watchdog
Interval
x
2
2
2
2
23
25
26
28
Table 6 Time-Out Values For Watchdog Timer
Hardware will set this flag on a power up condition. This flag can be read or written
by software. A write by software is the only way to clear this bit once it is set.
This bit is set by hardware to indicate that the time-out period has elapsed and
invoke watch dog timer interrupt if enabled(EWDI=1). This bit must be cleared by
software.
Hardware will set this bit when the watchdog timer causes a reset. Software can
read it but must clear it manually. A power-fail reset will also clear the bit. This bit
helps software in determining the cause of a reset. If EWT = 0, the watchdog timer
will have no affect on this bit.
Table 7 Watchdog Control WDCON SFR
Bit 5
0
-
268435456
Number of
33554462
67108864
8388608
Clocks
XXXX PRODUCT DESCRIPTION
Bit 4
x
-
26
Time@12MHz
22369.62 ms
2796.20 ms
5592.41 ms
699.05 ms
WDIF
Bit 3
0
Function
WTRF
Bit 2
x
Time@24MHz
11184.81 ms
2796.20 ms
1398.10 ms
349.53 ms
EWT
Bit 1
x
W681308
Rev1.2
Time@48MHz
1398.10 ms
5592.41 ms
174.76 ms
699.05 ms
RWT
Bit 0
0