MC68HC908GT16 Datasheet, PDF (72/412 Pages) Motorola, Inc – Microcontrollers

Resets and Interrupts
4.2 Introduction
Resets and interrupts are responses to exceptional events during
program execution. A reset re-initializes the MCU to its startup condition.
An interrupt vectors the program counter to a service routine.
4.3 Resets
A reset immediately returns the MCU to a known startup condition and
begins program execution from a user-defined memory location.
4.3.1 Effects
A reset:
• Immediately stops the operation of the instruction being executed
• Initializes certain control and status bits
• Loads the program counter with a user-defined reset vector
address from locations $FFFE and $FFFF
• Selects CGMXCLK divided by four as the bus clock
4.3.2 External Reset
A logic 0 applied to the RST pin for a time, t_IRL, generates an external
reset. An external reset sets the PIN bit in the SIM reset status register.
4.3.3 Internal Reset
Sources:
• Power-on reset (POR)
• Computer operating properly (COP)
• Low-power reset circuits
• Illegal opcode
• Illegal address
Technical Data
72
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
Resets and Interrupts
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