Low-Power Modes
Halt Mode
MC68HC05J1A — Rev. 3.0
Technical Data
MOTOROLA
Low-Power Modes
57
These conditions restart the CPU clock and bring the MCU out of wait
mode:
An external interrupt signal on the IRQ pin — A high-to-low
transition on the IRQ pin loads the program counter with the
contents of locations $07FA and $07FB.
An external interrupt signal on a port A external interrupt
pin — If the mask option for the port A external interrupt function
is selected, a low-to-high transition on a PA3–PA0 pin loads the
program counter with the contents of locations $07FA and $07FB.
A timer interrupt — A timer overflow or a real-time interrupt request
loads the program counter with the contents of locations $07F8
and $07F9.
A COP watchdog reset — A timeout of the mask-optional COP
watchdog resets the MCU and loads the program counter with the
contents of locations $07FE and $07FF. Software can enable
real-time interrupts so that the MCU can periodically exit wait
mode to reset the COP watchdog.
External reset — A logic 0 on the RESET pin resets the MCU and
loads the program counter with the contents of locations $07FE
and $07FF.
6.5 Halt Mode
If the mask option to disable the STOP instruction is selected, a STOP
instruction puts the MCU in halt mode. The halt mode is identical to the
wait mode, except that a recovery delay of 1–4064 internal clock cycles
occurs when the MCU exits the halt mode. If the mask option to disable
the STOP instruction is selected, the COP watchdog cannot be
inadvertently turned off by a STOP instruction.
Figure 6-1
shows the sequence of events in stop, wait, and halt modes.
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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