mc68hc908mr8 Freescale Semiconductor, Inc, mc68hc908mr8 Datasheet - Page 96

• Manufacturer Part Number: mc68hc908mr8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

System Integration Module (SIM)
7.4.2.1 Power-On Reset (POR)
Technical Data
96
The COP reset is asynchronous to the bus clock.
The active reset feature allows the part to issue a reset to peripherals
and other chips within a system built around the MCU.
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 the reset vector sequence to
occur.
At power-on, these events occur:
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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.
System Integration Module (SIM)
Figure 7-6. Sources of Internal Reset
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
POR
LVI
INTERNAL RESET
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor