Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
96 System Integration Module (SIM) MOTOROLA
System Integration Module (SIM)
7.4.2.1 Power-On Reset (POR)
When power is first applied to the MCU, the power-on reset (POR)
module generates a pulse to indicate that power-on has occurred. The
external reset pin (RST) is held low while the SIM counter counts out
4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles later, the CPU and
memories are released from reset to allow t he reset ve ctor sequence to
occur.
At power-on, these events occur:
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
CGMXCLK cycles to allow stabilization of the oscillator.
•The RST 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.
Figure 7-6. POR Recovery
PORRST
OSC1
CGMXCLK
CGMOUT
RST
IAB
4096
CYCLES 32
CYCLES 32
CYCLES
$FFFE $FFFF