Specifications

C8051F330/1
Rev. 1.1 91
10. 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 mem-
ory 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 pull-ups are enabled during and after
the reset. For VDD 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 internal oscillator.
Refer to
Section “13. Oscillators” on page 105 for information on selecting and configuring the system clock
source. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source (Section
“19.3. Watchdog Timer Mode” on page 194 details the use of the Watchdog Timer). Program execution begins at
location 0x0000.
PCA
WDT
Missing
Clock
Detector
(one-
shot)
(Software Reset)
System Reset
Reset
Funnel
Px.x
Px.x
EN
SWRSF
System
Clock
CIP-51
Microcontroller
Core
Extended Interrupt
Handler
EN
WDT
Enable
MCD
Enable
Errant
FLASH
Operation
/RST
(wired-OR)
Power On
Reset
'0'
+
-
Comparator 0
C0RSEF
VDD
+
-
Supply
Monitor
Enable
Figure 10.1. Reset Sources