
General Description
Pin Descriptions
M68HC11E Family — Rev. 5
Data Sheet
MOTOROLA
General Description
25
CAUTION:
In all cases, use caution around the oscillator pins. Load capacitances shown in the 
oscillator circuit are specified by the crystal manufacturer and should include all 
stray layout capacitances. 
Figure 1-9. Common Parallel Resonant Crystal Connections 
Figure 1-10. External Oscillator Connections 
1.4.4  E-Clock Output (E) 
E is the output connection for the internally generated E clock. The signal from E 
is used as a timing reference. The frequency of the E-clock output is one fourth that 
of the input frequency at the XTAL and EXTAL pins. When E-clock output is low, 
an internal process is taking place. When it is high, data is being accessed. 
All clocks, including the E clock, are halted when the MCU is in stop mode. To 
reduce RFI emissions, the E-clock output of most E-series devices can be disabled 
while operating in single-chip modes. 
The E-clock signal is always enabled on the MC68HC811E2. 
1.4.5  Interrupt Request (IRQ) 
The IRQ input provides a means of applying asynchronous interrupt requests to the 
MCU. Either negative edge-sensitive triggering or level-sensitive triggering is 
program selectable (OPTION register). IRQ is always configured to level-sensitive 
triggering at reset. When using IRQ in a level-sensitive wired-OR configuration, 
connect an external pullup resistor, typically 4.7 k
, to V
DD
. 
10 M
MCU
C
L
C
L
EXTAL
XTAL
4 x E
CRYSTAL
NC
MCU
EXTAL
XTAL
4 x E
CMOS-COMPATIBLE
EXTERNAL OSCILLATOR
F
Freescale Semiconductor, Inc.
For More Information On This Product,
  Go to: www.freescale.com
n
.