MC68HC908LJ24 Datasheet, PDF (147/464 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
System Integration Module (SIM)
Reset and System Initialization
OSC1
PORRST
ICLK
CGMOUT
RST
IRST
IAB
4096
CYCLES
32
CYCLES
32
CYCLES
Figure 9-7. POR Recovery
$FFFE
$FFFF
9.4.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of
the COP counter causes an internal reset and sets the COP bit in the
SIM reset status register (SRSR). The SIM actively pulls down the RST
pin for all internal reset sources.
To prevent a COP module timeout, write any value to location $FFFF.
Writing to location $FFFF clears the COP counter and bits 12 through 5
of the SIM counter. The SIM counter output, which occurs at least every
2¹³ – 2⁴ ICLK cycles, drives the COP counter. The COP should be
serviced as soon as possible out of reset to guarantee the maximum
amount of time before the first timeout.
The COP module is disabled if the RST pin or the IRQ pin is held at V_TST
while the MCU is in monitor mode. The COP module can be disabled
only through combinational logic conditioned with the high voltage signal
on the RST or the IRQ pin. This prevents the COP from becoming
disabled as a result of external noise. During a break state, V_TST on the
RST pin disables the COP module.
MC68HC908LJ24/LK24 — Rev. 2
MOTOROLA
System Integration Module (SIM)
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
147