AT83C51SND1C_03 ATMEL [ATMEL Corporation], AT83C51SND1C_03 Datasheet - Page 59

• Manufacturer Part Number: AT83C51SND1C_03
• Description: Single-Chip Flash Microcontroller with MP3 Decoder and Human Interface
• Manufacturer: ATMEL [ATMEL Corporation]

Watchdog Timer
Description
Figure 38. WDT Block Diagram
Watchdog Clock
Controller
Figure 39. WDT Clock Controller and Symbol
4109E–8051–06/03
System Reset
CLOCK
WDT
CLOCK
CLOCK
OSC
PER
RST
÷ 6
1Eh-E1h Decoder
÷
The AT8xC51SND1C implement a hardware Watchdog Timer (WDT) that automatically
resets the chip if it is allowed to time out. The WDT provides a means of recovering from
routines that do not complete successfully due to software or hardware malfunctions.
The WDT consists of a 14-bit prescaler followed by a 7-bit programmable counter. As
shown in Figure 38, the 14-bit prescaler is fed by the WDT clock detailed in
Section “Watchdog Clock Controller”, page 59.
The Watchdog Timer Reset register (WDTRST, see Table 67) provides control access
to the WDT, while the Watchdog Timer Program register (WDTPRG, see Figure 41) pro-
vides time-out period programming.
Three operations control the WDT:
•
•
•
As shown in Figure 39 the WDT clock (F
(F
These clocks are issued from the Clock Controller block as detailed in Section "Clock
Controller", page 12. When WTX2 bit is set, the WDT clock frequency is fixed and equal
to the oscillator clock frequency divided by 2. When cleared, the WDT clock frequency is
equal to the oscillator clock frequency divided by 2 in standard mode or to the oscillator
clock frequency in X2 mode.
2
WDTRST
PER
Chip reset clears and disables the WDT.
Programming the time-out value to the WDTPRG register.
Writing a specific 2-Byte sequence to the WDTRST register clears and enables the
WDT.
) or the oscillator clock (F
CKCON.6
WTX2
0
1
RST
MATCH
14-bit Prescaler
EN
WDT Clock
OSC
) depending on the WTX2 bit in CKCON register.
RST
CLOCK
OSC
7-bit Counter
WDT
WDTPRG.2:0
WTO2:0
) is derived from either the peripheral clock
SET
Pulse Generator
WDT Clock Symbol
OV
CLOCK
WDT
AT8xC51SND1C
To internal reset
RST
59