Datasheet

Computer Operating Properly (COP)
Technical Data MC68HC908AB32 — Rev. 1.1
354 Computer Operating Properly (COP) Freescale Semiconductor
20.3 Functional Description
Figure 20-1 shows the structure of the COP module.
Figure 20-1. COP Block Diagram
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
18
–2
4
or 2
13
–2
4
CGMXCLK cycles, depending on the state of the COP rate select bit,
COPRS, in configuration register 1. With a 2
18
–2
4
CGMXCLK cycle
overflow option, a 4.9152MHz crystal gives a COP timeout period of
53.3ms. 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.
NOTE: 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.
COPCTL WRITE
CGMXCLK
RESET VECTOR FETCH
RESET CIRCUIT
RESET STATUS REGISTER
INTERNAL RESET SOURCES
12-BIT COP PRESCALER
CLEAR ALL STAGES
6-BIT COP COUNTER
COP DISABLE
RESET
COPCTL WRITE
CLEAR
COP MODULE
COPEN (FROM SIM)
COP COUNTER
COP CLOCK
COP TIMEOUT
STOP INSTRUCTION
(COPD FROM CONFIG1)
COP RATE SEL
(COPRS FROM CONFIG1)
CLEAR STAGES 5–12