mc68hc908mr8 Freescale Semiconductor, Inc, mc68hc908mr8 Datasheet - Page 293

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

15.4 I/O Signals
15.4.1 CGMXCLK
15.4.2 COPCTL Write
15.4.3 Power-On Reset
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
NOTE:
The COP counter is a free-running, 6-bit counter preceded by the 13-bit
system integration module (SIM) counter. If not cleared by software, the
COP counter overflows and generates an asynchronous reset after
2
period is 53.3 ms. Writing any value to location $FFFF before overflow
occurs clears the COP counter and prevents reset.
A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the
COP bit in the SIM reset status register (SRSR) (see
Status
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.
This subsection describes the signals shown in
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency
is equal to the crystal frequency.
Writing any value to the COP control register (COPCTL) (see
Control
SIM counter. Reading the COP control register returns the reset vector.
The power-on reset (POR) circuit in the SIM clears the SIM counter 4096
CGMXCLK cycles after power-up.
18
–2
4
CGMXCLK cycles. With a 4.9152-MHz crystal, the COP timeout
Register).
Computer Operating Properly (COP)
Register) clears the COP counter and clears bits 12–4 of the
Computer Operating Properly (COP)
Figure
7.7.4 SIM Reset
15-1.
Technical Data
15.5 COP
I/O Signals
293