C8051F54X_14 Datasheet, PDF (129/275 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F54x
16. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this
reset state, the following occur:
 CIP-51 halts program execution
 Special Function Registers (SFRs) are initialized to their defined reset values
 External Port pins are forced to a known state
 Interrupts and timers are disabled.
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal
data memory are unaffected during a reset; any previously stored data is preserved. However, since the
stack pointer SFR is reset, the stack is effectively lost, even though the data on the stack is not altered.
The Port I/O latches are reset to 0xFF (all logic ones) in open-drain mode. Weak pullups are enabled dur-
ing and after the reset. For V_DD Monitor and power-on resets, the RST pin is driven low until the device
exits the reset state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the inter-
nal oscillator. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source. Pro-
gram execution begins at location 0x0000.
Px.x
Px.x
Comparator 0
+
-
C0RSEF
VDD
Supply
Monitor
+
-
Enable
Power On
Reset
'0'
(wired-OR)
/RST
Missing
Clock
Detector
(one-
shot)
EN
PCA
WDT
EN
Reset
Funnel
(Software Reset)
SWRSF
Errant
FLASH
Operation
System
Clock
CIP-51
Microcontroller ^{System Reset}
Core
Extended Interrupt
Handler
Figure 16.1. Reset Sources
Rev. 1.1
129