MC68HC05JJ6 Datasheet, PDF (60/216 Pages) Freescale Semiconductor, Inc – General Release Specification Microcontrollers

Resets
5.2 Introduction
This section describes the five reset sources and how they initialize the
MCU. A reset immediately stops the operation of the instruction being
executed, initializes certain control bits, and loads the program counter
with a user-defined reset vector address. These conditions produce a
reset:
• Initial power-up of device (power-on reset)
• A logic zero applied to the RESET pin (external reset)
• Timeout of the COP watchdog (COP reset)
• Low voltage applied to the device (LVR reset)
• Fetch of an opcode from an address not in the memory map
(illegal address reset)
Figure 5-1 shows a block diagram of the reset sources and their
interaction.
LVR MASK OPTION
(ENABLE = 1)
COP MASK OPTION
(ENABLE = 1)
V_DD
RESET
COP WATCHDOG
LOW-VOLTAGE RESET
POWER-ON RESET
ILLEGAL ADDRESS RESET
INTERNAL
ADDRESS BUS
3-CYCLE
CLOCKED
1-SHOT
S
D
RST
RESET
LATCH
R
TO CPU
AND
SUBSYSTEMS
INTERNAL
CLOCK
Figure 5-1. Reset Sources
General Release Specification
60
Resets
MC68HC05JJ6/MC68HC05JP6 — Rev. 3.2
Freescale Semiconductor