MC68HC705J2 Datasheet, PDF (29/82 Pages) Freescale Semiconductor, Inc – member of the low-cost

Freescale Semiconductor, Inc.
4.3.2 WAIT Mode
The WAIT instruction puts the MCU in an intermediate power-consumption mode.
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In WAIT mode, the following events occur:
• All CPU clocks stop.
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• The CPU clears the interrupt mask in the condition code register, enabling
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external interrupts and timer interrupts.
The WAIT instruction does not affect any other registers or any I/O lines. The timer
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and COP timer remain active in WAIT mode.
The following conditions bring the MCU out of WAIT mode:
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• A timer interrupt. If a real-time interrupt or a timer overflow interrupt occurs
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during WAIT mode, the MCU loads the program counter with the contents of
locations $0FF8 and $0FF9, the locations of the vector address of the timer
interrupt service routine.
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• An external interrupt. An external interrupt automatically loads the program
counter with the contents of locations $0FFA and $0FFB, the locations of the
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vector address of the external interrupt service routine.
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• A COP timer reset. A timeout of the COP timer during WAIT mode resets
the MCU. The programmer can enable real-time interrupts so the MCU can
periodically exit WAIT mode to reset the COP timer.
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• A reset signal on the RESET pin during WAIT mode resets the MCU.
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A COP timer reset or a reset signal on the RESET pin automatically loads the
program counter with the contents of locations $0FFE and $0FFF, the locations of
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the vector address of the reset service routine.
Figure 4-3 shows the sequence of events caused by the WAIT instruction.
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CENTRAL PROCESSOR UNIT
Rev. 2
4-7
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