MC68HC705T16 MOTOROLA [Motorola, Inc], MC68HC705T16 Datasheet - Page 31

• Manufacturer Part Number: MC68HC705T16
• Description: High-density complementary metal oxide semiconductor (HCMOS) microcontroller unit
• Manufacturer: MOTOROLA [Motorola, Inc]

4.1
The MC68HC05T16 can be reset in three ways: by the initial power-on reset function, by an active
low input to the RESET pin, and by a COP watchdog timer reset (if enabled). Any of these resets
will cause the program to go to its starting address, specified by the contents of memory locations
$FFFE and $FFFF, and cause the interrupt mask of the Condition Code register to be set.
4.1.1
The power-on reset occurs when a positive transition is detected on the supply voltage, V
power-on reset is used strictly for power-up conditions, and should not be used to detect any drops
in the power supply voltage. There is no provision for a power-down reset. The power-on circuitry
provides for a 4064 tcyc delay from the time that the oscillator becomes active. If the external
RESET pin is low at the end of the 4064 tcyc time out, the processor remains in the reset condition
until RESET goes high. The user must ensure that V
operate properly prior to the time the 4064 POR cycles have elapsed. If there is doubt, the external
RESET pin should remain low until such time that V
specified.
4.1.2
The RESET input pin is used to reset the MCU to provide an orderly software start-up procedure.
When using the external reset, the RESET pin must stay low for a minimum of 1.5tcyc. The
RESET pin contains an internal Schmitt Trigger as part of its input to improve noise immunity.
MC68HC05T16
RESETS
Power-On Reset (POR)
RESET Pin
RESETS AND INTERRUPTS
RESETS AND INTERRUPTS
4
DD
DD
has risen to the minimum operating voltage
has risen to a point where the MCU can
MOTOROLA
DD
. The
TPG
4-1
4