mc68hc05pl4b Freescale Semiconductor, Inc, mc68hc05pl4b Datasheet - Page 33

• Manufacturer Part Number: mc68hc05pl4b
• Description: Low-cost Single-chip Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.1
MC68HC05PL4
REV 2.0
RESET
V
DD
This section describes the four 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 de ned reset v ec-
tor address. The following conditions produce a reset:
POWER-ON RESET
A positive transition on the V
reset is strictly for conditions during powering up and cannot be used to detect
drops in power supply voltage.
•
•
•
•
Initial power-up of device (power-on reset)
A logic zero applied to the RESET pin (external reset)
Time-out of the COP watchdog (COP reset)
Fetch of an opcode from an address not in the memory map
(illegal address reset)
ILLEGAL ADDRESS RESET
POWER-ON RESET
COUNTER
COP WATCHDOG
4-CYCLE
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure 5-1. Reset Sources
INTERNAL
ADDRESS BUS
Go to: www.freescale.com
DD
SECTION 5
April 30, 1998
RESETS
pin generates a power on reset. The power-on
RESETS
GENERAL RELEASE SPECIFICATION
D
RESET
LATCH
S
R
RST
TO CPU
AND
SUBSYSTEMS
INTERNAL
CLOCK
5-1