MC68HC908JK1 Datasheet, PDF (175/210 Pages) Motorola, Inc – MC68HC908JK1

Computer Operating Properly (COP)
I/O Signals
NOTE:
Service the COP immediately after reset and before entering or after
exiting stop mode to guarantee the maximum time before the first COP
counter overflow.
A COP reset pulls the RST pin low for 32 × 2OSCOUT cycles and sets
the COP bit in the reset status register (RSR). (See 7.8.2 Reset Status
Register (RSR).).
NOTE:
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.
15.4 I/O Signals
The following paragraphs describe the signals shown in Figure 15-1.
15.4.1 2OSCOUT
2OSCOUT is the oscillator output signal. 2OSCOUT frequency is equal
to the crystal frequency or the RC-oscillator frequency.
15.4.2 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 15.5 COP
Control Register) clears the COP counter and clears bits 12 through 5
of the SIM counter. Reading the COP control register returns the low
byte of the reset vector.
15.4.3 Power-On Reset
The power-on reset (POR) circuit in the SIM clears the SIM counter
4096 × 2OSCOUT cycles after power-up.
15.4.4 Internal Reset
An internal reset clears the SIM counter and the COP counter.
MC68H(R)C908JL3 — Rev. 1.0
MOTOROLA
Computer Operating Properly (COP)
Technical Data
175