MC68HC705KJ1 Datasheet, PDF (71/108 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Chapter 8
Resets and Interrupts
8.1 Introduction
Reset initializes the MCU by returning the program counter to a known address and by forcing control and
status bits to known states.
Interrupts temporarily change the sequence of program execution to respond to events that occur during
processing.
8.2 Resets
A reset immediately stops the operation of the instruction being executed, initializes certain control and
status bits, and loads the program counter with a user-defined reset vector address. The following
sources can generate a reset:
• Power-on reset (POR) circuit
• RESET pin
• Computer operating properly (COP) watchdog
• Illegal address
V_DD
RESET PIN
ILLEGAL ADDRESS
COP WATCHDOG
POWER-ON RESET
INTERNAL CLOCK
S RST
D
Q
CK
RESET
LATCH
TO CPU AND
PERIPHERAL
MODULES
Figure 8-1. Reset Sources
MC68HC705KJ1 • MC68HRC705KJ1 • MC68HLC705KJ1 Data Sheet, Rev. 4.1
Freescale Semiconductor
71