MC68HC05K1 FREESCALE [Freescale Semiconductor, Inc], MC68HC05K1 Datasheet - Page 57

• Manufacturer Part Number: MC68HC05K1
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

5.3.5 Low-Voltage Reset
5.4 Reset States
5.4.1 CPU
MC68HC05K0 • MC68HC05K1 — Rev. 2.0
NOTE:
The low-voltage reset circuit is a mask option that generates a reset
signal if the voltage on the V
must be set at 5 V 10% if the mask option enabling the low-voltage
reset circuit is selected.
A low-voltage reset pulls the RESET pin low for as long as the
low-voltage condition exists.
When the low-voltage reset is enabled, use a pullup resistor on RESET
because low-voltage reset shorts RESET to ground when it detects a
low V
V
being pulled down by the short. V
permanently damage the chip.
This subsection describes how resets initialize the MCU.
A reset has these effects on the CPU:
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Freescale Semiconductor, Inc.
to ground, causing the chip to possibly remain in reset due to V
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Loads the stack pointer with $FF
Sets the I bit in the condition code register, inhibiting interrupts
Sets the IRQE bit in the interrupt status and control register
Loads the program counter with the user-defined reset vector from
locations $03FE and $03FF
Clears the IRQF bit (IRQ latch)
Clears the stop latch, enabling the CPU clock, or exiting the halt
mode
Clears the wait latch, waking the CPU from wait mode
. If there is no pullup to limit current, low-voltage reset will short
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Resets
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pin falls below the LVR trip point. V
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may also pull current and
Technical Data
Reset States
Resets
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