MC9RS08KA8RM Datasheet, PDF (41/190 Pages) Freescale Semiconductor, Inc – MC9RS08KA8 Features

Chapter 5
Resets, Interrupts, and General System Control
5.1 Introduction
This chapter discusses basic reset, interrupt mechanisms, and the various reset and interrupt sources in the
MC9RS08KA8 series. Some interrupt sources from peripheral modules are discussed in detail in other
chapters of this reference manual. This chapter gathers basic information about all reset and interrupt
sources in one place for easy reference. A few reset and wakeup sources, including the computer operating
properly (COP) watchdog and real-time interrupt (RTI), are not part of on-chip peripheral systems with
their own chapters but are part of the system control logic.
5.2 Features
Reset and interrupt features include:
• Multiple sources of reset for flexible system configuration and reliable operation
• System reset status register (SRS) to indicate the source of the most recent reset
• System interrupt pending register (SIP1) to indicate the status of pending system interrupts
— Analog comparator interrupt with enable
— Keyboard interrupt with enable
— Modulo timer interrupt with enable
— Real-time interrupt with enable
— ADC interrupt with enable
— IIC interrupt with enable
— TPM interrupt with enable
5.3 MCU Reset
Resetting the MCU provides a way to start processing from a known set of conditions. During reset, most
control and status registers are forced to initial values, and the program counter is started from location
$3FFD. A JMP instruction (opcode $BC) with operand located at $3FFE – $3FFF must be programmed
into the user application for correct reset operation. The operand defines the location at which the user
program starts. On-chip peripheral modules are disabled and I/O pins are initially configured as
general-purpose, high-impedance inputs with pullup/pulldown devices disabled.
The MC9RS08KA8 series has seven reset sources:
• External pin reset (PIN) — Enabled using RSTPE in SOPT
• Power-on reset (POR)
MC9RS08KA8 Series Reference Manual, Rev. 3
Freescale Semiconductor
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