mc68hc908gr8b Freescale Semiconductor, Inc, mc68hc908gr8b Datasheet - Page 79

• Manufacturer Part Number: mc68hc908gr8b
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

COP Control Register
6.3.7 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register. See
Chapter 5 Configuration Register (CONFIG).
6.4 COP Control Register
The COP control register (COPCTL) is located at address $FFFF and overlaps the reset vector. Writing
any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF
returns the low byte of the reset vector.
Address: $FFFF
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
Figure 6-2. COP Control Register (COPCTL)
6.5 Interrupts
The COP does not generate central processor unit (CPU) interrupt requests.
6.6 Monitor Mode
When monitor mode is entered with V
on the IRQ pin, the COP is disabled as long as V
remains
TST
TST
on the IRQ pin or the RST pin. When monitor mode is entered by having blank reset vectors and not
having V
on the IRQ pin, the COP is automatically disabled until a POR occurs.
TST
6.7 Low-Power Modes
The WAIT and STOP instructions put the microcontroller unit (MCU) in low power-consumption standby
modes.
6.7.1 Wait Mode
The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout.
6.7.2 Stop Mode
Stop mode turns off the CGMXCLK input to the COP and clears the COP prescaler. Service the COP
immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering
or exiting stop mode.
To prevent inadvertently turning off the COP with a STOP instruction, a configuration option is available
that disables the STOP instruction. When the STOP bit in the configuration register has the STOP
instruction disabled, execution of a STOP instruction results in an illegal opcode reset.
6.8 COP Module During Break Mode
The COP is disabled during a break interrupt when V
is present on the RST pin.
TST
MC68HC908GR8B Data Sheet, Rev. 3.0
Freescale Semiconductor
79