Timing System
Computer Operating Properly (COP) Watchdog Function
MC68HC11E Family
—
Rev. 4
Technical Data
MOTOROLA
Timing System
203
9.7 Computer Operating Properly (COP) Watchdog Function
The clocking chain for the COP function, tapped off of the main timer
divider chain, is only superficially related to the main timer system. The
CR[1:0] bits in the OPTION register and the NOCOP bit in the CONFIG
register determine the status of the COP function. One additional
register, COPRST, is used to arm and clear the COP watchdog reset
system. Refer to
Section 5. Resets and Interrupts
for a more detailed
discussion of the COP function.
9.8 Pulse Accumulator
The M68HC11 Family of MCUs has an 8-bit counter that can be
configured to operate either as a simple event counter or for gated time
accumulation, depending on the state of the PAMOD bit in the PACTL
register. Refer to the pulse accumulator block diagram,
Figure 9-24
. In
the event counting mode, the 8-bit counter is clocked to increasing
values by an external pin. The maximum clocking rate for the external
event counting mode is the E clock divided by two. In gated time
accumulation mode, a free-running E-clock divide-by-64 signal drives
the 8-bit counter, but only while the external PAI pin is activated. Refer to
Table 9-6
. The pulse accumulator counter can be read or written at any
time.