mc68hc908gp20 Freescale Semiconductor, Inc, mc68hc908gp20 Datasheet - Page 295

• Manufacturer Part Number: mc68hc908gp20
• Description: M68hc08 Family Of 8-bit Microcontroller Units Mcus
• Manufacturer: Freescale Semiconductor, Inc

19.4.2.1 Power-On Reset
MC68HC908GP20
Freescale Semiconductor
CGMXCLK
CGMOUT
PORRST
OSC1
RST
IAB
—
Rev 2.1
When power is first applied to the MCU, the power-on reset module
(POR) 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 the reset vector sequence to
occur.
At power-on, these events occur:
CYCLES
•
•
•
•
•
•
4096
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 19-7. POR Recovery
CYCLES
32
CYCLES
32
$FFFE
Advance Information
$FFFF
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