Freescale Semiconductor MC68HC08KH12 - Manual (Page 68)

Advance Information MC68HC(7)08KH12 — Rev. 1.1
68 Freescale Semiconductor
Figure 7-5. Internal Reset Timing
The COP reset is asynchronous to the bus clock.
Figure 7-6. Sources of Internal Reset
The active reset feature allows the part to issue a reset to peripherals
and other chips within a system built around the MCU.
7.4.2.1 Power-On Reset
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, the following events occur:
• A POR pulse is generated.
• The internal reset signal is asserted.
• The SIM enables the oscillator to drive CGMXCLK.
• 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 reset status register (RSR) is set and all other
bits in the register are cleared.
IRST
RST RST PULLED LOW BY MCU
IAB
32 CYCLES 32 CYCLES
VECTOR HIGH
CGMXCLK
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
POR
INTERNAL RESET
USB