XC908AS60ACFU Motorola Semiconductor Products, XC908AS60ACFU Datasheet - Page 156

• Manufacturer Part Number: XC908AS60ACFU
• Description: MC68HC908AZ60A, MC68HC908AS60A Hcmos Microcontroller Unit Technical Data
• Manufacturer: Motorola Semiconductor Products

System Integration Module (SIM)
9.4.2.5 Low-Voltage Inhibit (LVI) Reset
9.5 SIM Counter
9.5.1 SIM Counter During Power-On Reset
Technical Data
156
NOTE:
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.
Extra care should be exercised if code in this part has been
migrated from older HC08 devices since the illegal address reset
specification may be different. Also, extra care should be exercised
when using this emulation part for development of code to be run
in ROM AZ, AB or AS family parts with a smaller memory size since
some legal addresses will become illegal addresses on the smaller
ROM memory map device and may as a result generate unwanted
resets.
The low-voltage inhibit module (LVI) asserts its output to the SIM when
the V
status register (SRSR) is set and a chip reset is asserted if the LVIPWRD
and LVIRSTD bits in the CONFIG-1 register are at logic zero. The RST
pin will be held low until the SIM counts 4096 CGMXCLK cycles after
V
CPU is released from reset to allow the reset vector sequence to occur.
See
The SIM counter is used by the power-on reset module (POR) and in
stop mode recovery to allow the oscillator time to stabilize before
enabling the internal bus (IBUS) clocks. The SIM counter also serves as
a prescaler for the computer operating properly module (COP). The SIM
counter overflow supplies the clock for the COP module. The SIM
counter is 12 bits long and is clocked by the falling edge of CGMXCLK.
The power-on reset module (POR) detects power applied to the MCU.
At power-on, the POR circuit asserts the signal PORRST. Once the SIM
DD
rises above V
Low Voltage Inhibit (LVI)
DD
voltage falls to the V
System Integration Module (SIM)
LVIR
. Another sixty-four CGMXCLK cycles later, the
LVII
on page 229.
voltage. The LVI bit in the SIM reset
MC68HC908AZ60A — Rev 2.0
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