XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 30

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

General Description
1.6.3.5 XIRQ
1.6.3.6 SMODN, MODA, and MODB
1.6.3.7 BKGD
Data Sheet
30
NOTE:
XIRQ is the non-maskable external interrupt pin. It provides a means of requesting
a non-maskable 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 pullup on this pin while in reset and immediately out of
reset. The pullup can be turned off by clearing the PUPE bit in the pullup control
register (PUCR). XIRQ is often used as a power loss detect interrupt.
When 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 recognizes another interrupt as soon as the interrupt
mask bit in the MCU is cleared, normally upon return from an interrupt.
SMODN, MODA, and MODB are the mode-select signals. Their state during reset
determines the MCU operating mode. After reset, MODA and MODB can be
configured as instruction queue tracking signals IPIPE0 and IPIPE1. MODA and
MODB have active pulldowns during reset.
The SMODN pin can be used as BKGD or TAGHI after reset.
To aid in mode selection, refer to
are provided as suggestive layouts only.
BKGD is the single-wire background mode pin. It receives and transmits serial
background debugging commands. A special self-timing protocol is used. The
BKGD pin has an active pullup when configured as input; BKGD has no pullup
control. Currently, the tool connection configuration shown in
General Description
Figure 1-7. BDM Tool Connector
BKGD
Figure 1-8
V
NC
FP
1
3
5
2
4
6
and
GND
RESET
V
DD
Figure
M68HC12B Family — Rev. 8.0
1-9. These schematics
Figure 1-7
MOTOROLA
is used.