MC9S08DN60 Datasheet, PDF (63/354 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 5
Resets, Interrupts, and General System Control
5.1 Introduction
This section discusses basic reset and interrupt mechanisms and their various sources in the MC9S08DN60
Series. Some interrupt sources from peripheral modules are discussed in greater detail within other
sections of this data sheet. This section gathers basic information about all reset and interrupt sources in
one place for easy reference. A few reset and interrupt sources, including the computer operating properly
(COP) watchdog, are not part of on-chip peripheral systems with their own chapters.
5.2 Features
Reset and interrupt features include:
• Multiple sources of reset for flexible system configuration and reliable operation
• Reset status register (SRS) to indicate source of most recent reset
• Separate interrupt vector for each module (reduces polling overhead); see Table 5-1
5.3 MCU Reset
Resetting the MCU provides a way to start processing from a known set of initial conditions. During reset,
most control and status registers are forced to initial values and the program counter is loaded from the
reset vector (0xFFFE:0xFFFF). On-chip peripheral modules are disabled and I/O pins are initially
configured as general-purpose high-impedance inputs with pull-up devices disabled. The I bit in the
condition code register (CCR) is set to block maskable interrupts so the user program has a chance to
initialize the stack pointer (SP) and system control settings. (See the CPU chapter for information on the
Interrupt (I) bit.) SP is forced to 0x00FF at reset.
The MC9S08DN60 Series has eight sources for reset:
• Power-on reset (POR)
• External pin reset (PIN)
• Computer operating properly (COP) timer
• Illegal opcode detect (ILOP)
• Illegal address detect (ILAD)
• Low-voltage detect (LVD)
• Loss of clock (LOC)
• Background debug forced reset (BDFR)
Each of these sources, with the exception of the background debug forced reset, has an associated bit in
the system reset status register (SRS).
MC9S08DN60 Series Data Sheet, Rev 2
Freescale Semiconductor
63