mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 102

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
At power-on, these events occur:
7.3.2.2 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 2
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 IRQ1 pin is held at V
mode. The COP module can be disabled only through combinational logic conditioned with the high
voltage signal on the RST or the IRQ1 pin. This prevents the COP from becoming disabled as a result of
external noise. During a break state, V
7.3.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP
bit in the SIM reset status register (SRSR) and causes a reset.
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CGMOUT
A POR pulse is generated.
The internal reset signal is asserted.
The SIM enables CGMOUT.
Internal clocks to the CPU and modules are held inactive for 4096 ICLK cycles to allow stabilization
of the oscillator.
The pin is driven low during the oscillator stabilization time.
The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are
cleared.
PORRST
13
OSC1
ICLK
IRST
– 2
RST
IAB
4
ICLK cycles, drives the COP counter. The COP should be serviced as soon as possible
CYCLES
4096
MC68HC908AP A-Family Data Sheet, Rev. 3
Figure 7-7. POR Recovery
TST
CYCLES
32
on the RST pin disables the COP module.
CYCLES
32
TST
$FFFE
while the MCU is in monitor
Freescale Semiconductor
$FFFF