mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 258

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Computer Operating Properly (COP)
19.3 Functional Description
Data Sheet
258
INTERNAL RESET SOURCES
(COPRS FROM CONFIG1)
(COPD FROM CONFIG1)
RESET VECTOR FETCH
STOP INSTRUCTION
COPEN (FROM SIM)
NOTE:
COP RATE SEL
COPCTL WRITE
COPCTL WRITE
COP DISABLE
OSCXCLK
RESET
Figure 19-1
The COP counter is a free-running 6-bit counter preceded by a 12-bit
prescaler counter. If not cleared by software, the COP counter overflows
and generates an asynchronous reset after 2
OSCXCLK cycles, depending on the state of the COP rate select bit,
COPRS, in configuration register 1. With a 2
overflow option, a 24MHz crystal gives a COP timeout period of
10.922ms. Writing any value to location $FFFF before an overflow
occurs prevents a COP reset by clearing the COP counter and stages
12 through 5 of the prescaler.
Service the COP immediately after reset and before entering or after
exiting stop mode to guarantee the maximum time before the first COP
counter overflow.
Figure 19-1. COP Block Diagram
COP MODULE
COP CLOCK
12-BIT COP PRESCALER
Computer Operating Properly (COP)
shows the structure of the COP module.
COP COUNTER
6-BIT COP COUNTER
CLEAR
RESET STATUS REGISTER
18
18
MC68HC908BD48
– 2
RESET CIRCUIT
– 2
4
Freescale Semiconductor
4
OSCXCLK cycle
or 2
13
– 2
4
—
Rev. 2.1