mc68hc11d0 Freescale Semiconductor, Inc, mc68hc11d0 Datasheet - Page 16

• Manufacturer Part Number: mc68hc11d0
• Description: Mc68hc11d0 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

2.4 E-Clock Output (E)
2.5 Interrupt Request (IRQ)
2.6 Non-Maskable Interrupt (XIRQ)
2-4
*
FIRST
MCU
THIS VALUE INCLUDES ALL STRAY CAPACITANCES.
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 in-
ternal process is taking place. When it is high, data is being accessed. All clocks, in-
cluding the E clock, are halted when the MCU is in STOP mode. The E clock can be
turned off in single-chip modes to reduce the effects of radio frequency interference
(RFI).
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. Connect an external pullup resistor, typically 4.7 k , to V
in a level sensitive wired-OR configuration.
The XIRQ input provides a means of requesting a nonmaskable interrupt after reset
initialization. During reset, the X bit in the condition code register (CCR) is set and any
interrupt is masked until MCU software enables it. Because the XIRQ input is level-
EXTAL
XTAL
MCU
Figure 2-5 External Oscillator Connections
Figure 2-6 One Crystal Driving Two MCUs
EXTAL
10 M
XTAL
Freescale Semiconductor, Inc.
For More Information On This Product,
NC
Go to: www.freescale.com
CRYSTAL
4 x E
PIN DESCRIPTIONS
25 pF
25 pF
EXTERNAL OSCILLATOR
*
*
CMOS-COMPATIBLE
4 x E
EXT EXTAL CONN
220
DD
when IRQ is used
NC
TECHNICAL DATA
DUAL-MCU XTAL CONN
EXTAL
XTAL
SECOND
MCU