Samsung S3C2451X User Manual page 70

SYSTEM CONTROLLER
POWER
nRESET
EXTCLK
or XTIpll
Clock
disable
VCO
output
SYSCLK
WATCHDOG RESET
Watchdog reset is invoked when software fails to prevent the watchdog timer from timing out.
During the watchdog reset, the following actions occur :
•
All units(except some blocks listed in table 2-1 ) go into their pre-defined reset state.
•
All pins get their reset state, and BATT_FLT pin is ignored.
•
The nRSTOUT pin is asserted during watchdog reset.
Watchdog reset can be activated in normal and idle mode because watchdog timer can expire with clock.
Watchdog reset is invoked when watchdog timer and reset are enabled (WTCON[5] = 1, WTCON[0]=1) and
watchdog timer is expired. Watchdog reset is invoked then, the following sequence occurs. :
1. Watchdog reset source asserts.
2. Internal reset signals and nRSTOUT are asserted and reset counter is activated.
3. Reset counter is expired then, internal reset signals and nRSTOUT are deasserted.
Preliminary product information describe products that are in development,
2-4
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
The logic is operarted by
EXTCLK or XTIpll
Figure 2-2. Power-on reset sequence
S3C2451X RISC MICROPROCESSOR
PLL is configured by S/W first time
Lock time
VCO is adapte to new clock frequency
.
SYSCLK is FOUT