MC68HC08JB1 Datasheet, PDF (83/216 Pages) Motorola, Inc – Microcontrollers

8.4.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An
illegal instruction sets the ILOP bit in the reset status register (RSR) and
causes a reset.
If the stop enable bit, STOP, in the mask option register is logic 0, the
SIM treats the STOP instruction as an illegal opcode and causes an
illegal opcode reset. The SIM actively pulls down the RST pin for all
internal reset sources.
8.4.2.4 Illegal Address Reset
An opcode fetch from an unmapped address generates an illegal
address reset. The SIM verifies that the CPU is fetching an opcode prior
to asserting the ILAD bit in the reset status register (RSR) and resetting
the MCU. A data fetch from an unmapped address does not generate a
reset. The SIM actively pulls down the RST pin for all internal reset
sources.
8.4.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when
the V_DD voltage falls to the LVI reset voltage, V_TRIP. The LVI bit in the
reset status register (RSR) is set, and the external reset pin (RST) is held
low while the SIM counter counts out 4096 OSCXCLK cycles. Sixty-four
OSCXCLK cycles later, the CPU is released from reset to allow the reset
vector sequence to occur. The SIM actively pulls down the RST pin for
all internal reset sources.
8.4.2.6 Universal Serial Bus Reset
The USB module will detect a reset signaled on the bus by the presence
of an extended SE0 at the USB data pins of a device. The MCU seeing
a single-ended 0 on its USB data inputs for more than 2.5µs treats that
signal as a reset. After the reset is removed, the device will be in the
attached, but not yet addressed or configured, state (refer to Section 9.1
USB Devices of the Universal Serial Bus Specification Rev. 1.1). The
device must be able to accept the device address via a SET_ADDRESS
MC68HC08JB1 — Rev. 2.1
Freescale Semiconductor
Technical Data
83