MC68HC908JB8 Datasheet, PDF (102/286 Pages) Motorola, Inc – MICROCONTROLLERS

System Integration Module (SIM)
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
command (refer to Section 9.4 of the Universal Serial Bus Specification
Rev. 1.1) no later than 10ms after the reset is removed.
USB reset can be disabled to generate an internal reset, instead, a USB
interrupt can be generated. (See Section 5. Configuration Register
(CONFIG).)
NOTE: USB reset is disabled when the USB module is disabled by clearing the
USBEN bit of the USB Address Register (UADDR).
8.4.2.7 Registers Values After Different Resets
Some registers are reset by POR or LVI reset only. Table 8-3 shows the
registers or register bits which are unaffected by normal resets.
Technical Data
102
MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3
System Integration Module (SIM)
Freescale Semiconductor