MC912DG128A Motorola, MC912DG128A Datasheet - Page 36

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

Maskable
Interrupt Request
(IRQ)
Nonmaskable
Interrupt (XIRQ)
Mode Select
(SMODN, MODA,
and MODB)
Pinout and Signal Descriptions
MC68HC912DT128A Rev 2.0
36
The IRQ input provides a means of applying asynchronous interrupt
requests to the MCU. Either falling edge-sensitive triggering or
level-sensitive triggering is program selectable (INTCR register). IRQ is
always enabled and configured to level-sensitive triggering at reset. It
can be disabled by clearing IRQEN bit (INTCR register). When the MCU
is reset the IRQ function is masked in the condition code register. This
pin is always an input and can always be read. There is an active pull-up
on this pin while in reset and immediately out of reset. The pullup can be
turned off by clearing PUPE in the PUCR register.
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 sensitive, it can be connected
to a multiple-source wired-OR network. This pin is always an input and
can always be read. There is an active pull-up on this pin while in reset
and immediately out of reset. The pullup can be turned off by clearing
PUPE in the PUCR register. XIRQ is often used as a power loss detect
interrupt.
Whenever XIRQ or IRQ are used with multiple interrupt sources (IRQ
must be configured for level-sensitive operation if there is more than one
source of IRQ interrupt), each source must drive the interrupt input with
an open-drain type of driver to avoid contention between outputs. There
must also be an interlock mechanism at each interrupt source so that the
source holds the interrupt line low until the MCU recognizes and
acknowledges the interrupt request. If the interrupt line is held low, the
MCU will recognize another interrupt as soon as the interrupt mask bit in
the MCU is cleared (normally upon return from an interrupt).
The state of these pins during reset determine the MCU operating mode.
After reset, MODA and MODB can be configured as instruction queue
tracking signals IPIPE0 and IPIPE1 in expanded modes. MODA and
MODB have active pulldowns during reset.
The SMODN pin has an active pullup when configured as an input. The
pin can be used as BKGD or TAGHI after reset.
Pinout and Signal Descriptions
MOTOROLA
10-pins