MC68HC711E9CFU2 Freescale Semiconductor, MC68HC711E9CFU2 Datasheet - Page 127
Manufacturer Part Number
IC MCU 12K OTP 2MHZ 64-QFP
Specifications of MC68HC711E9CFU2
Number Of I /o
Program Memory Size
12KB (12K x 8)
Program Memory Type
512 x 8
512 x 8
Voltage - Supply (vcc/vdd)
4.5 V ~ 5.5 V
-40°C ~ 85°C
Package / Case
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
The M68HC11 timing system is composed of five clock divider chains. The main clock divider chain
includes a 16-bit free-running counter, which is driven by a programmable prescaler. The main timer’s
programmable prescaler provides one of the four clocking rates to drive the 16-bit counter. Two prescaler
control bits select the prescale rate.
The prescaler output divides the system clock by 1, 4, 8, or 16. Taps off of this main clocking chain drive
circuitry that generates the slower clocks used by the pulse accumulator, the real-time interrupt (RTI), and
the computer operating properly (COP) watchdog subsystems, also described in this section. Refer to
All main timer system activities are referenced to this free-running counter. The counter begins
incrementing from $0000 as the MCU comes out of reset and continues to the maximum count, $FFFF.
At the maximum count, the counter rolls over to $0000, sets an overflow flag, and continues to increment.
As long as the MCU is running in a normal operating mode, there is no way to reset, change, or interrupt
the counting. The capture/compare subsystem features three input capture channels, four output
compare channels, and one channel that can be selected to perform either input capture or output
compare. Each of the three input capture functions has its own 16-bit input capture register (time capture
latch) and each of the output compare functions has its own 16-bit compare register. All timer functions,
including the timer overflow and RTI, have their own interrupt controls and separate interrupt vectors.
The pulse accumulator contains an 8-bit counter and edge select logic. The pulse accumulator can
operate in either event counting mode or gated time accumulation mode. During event counting mode,
the pulse accumulator’s 8-bit counter increments when a specified edge is detected on an input signal.
During gated time accumulation mode, an internal clock source increments the 8-bit counter while an
input signal has a predetermined logic level.
The real-time interrupt (RTI) is a programmable periodic interrupt circuit that permits pacing the execution
of software routines by selecting one of four interrupt rates.
The COP watchdog clock input (E ÷ 2
) is tapped off of the free-running counter chain. The COP
automatically times out unless it is serviced within a specific time by a program reset sequence. If the COP
is allowed to time out, a reset is generated, which drives the RESET pin low to reset the MCU and the
external system. Refer to
for crystal-related frequencies and periods.
M68HC11E Family Data Sheet, Rev. 5.1