mc68hc908ld64 Freescale Semiconductor, Inc, mc68hc908ld64 Datasheet - Page 331

• Manufacturer Part Number: mc68hc908ld64
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

22.4 I/O Signals
22.4.1 OSCXCLK
22.4.2 STOP Instruction
22.4.3 COPCTL Write
22.4.4 Power-On Reset
MC68HC908LD64
Freescale Semiconductor
NOTE:
—
Rev. 3.0
A COP reset pulls the RST pin low for 32 OSCXCLK cycles and sets the
COP bit in the SIM reset status register (SRSR).
In monitor mode, the COP is disabled if the RST pin or the IRQ is held
at V
Place COP clearing instructions in the main program and not in an
interrupt subroutine. Such an interrupt subroutine could keep the COP
from generating a reset even while the main program is not working
properly.
The following paragraphs describe the signals shown in
OSCXCLK is the crystal oscillator output signal. OSCXCLK frequency is
equal to the crystal frequency.
The STOP instruction clears the COP prescaler.
Writing any value to the COP control register (COPCTL) (see
Control
of the prescaler. Reading the COP control register returns the low byte
of the reset vector.
The power-on reset (POR) circuit clears the COP prescaler 4096
OSCXCLK cycles after power-up.
TST
. During the break state, V
Computer Operating Properly (COP)
Register) clears the COP counter and clears bits 12 through 5
TST
on the RST pin disables the COP.
Computer Operating Properly (COP)
Figure
22.5 COP
Data Sheet
I/O Signals
22-1.
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