L
G
R
Interrupts
General Release Specification
MC68HC(7)05H12
—
Rev. 1.0
64
Interrupts
MOTOROLA
Either a level-sensitive and edge-sensitive trigger, or an edge-sensitive-
only trigger can be implemented by software.
NOTE:
The internal interrupt latch is cleared in the first part of the interrupt
service routine; therefore, one external interrupt pulse could be latched
and serviced as soon as the I bit is cleared.
The BIH and BIL instructions will only apply to the level on the IRQ pin
itself, and not to the output of the logic OR function with the Port A
keyboard wakeup interrupts. The state of the individual Port A pins can
be checked by reading the appropriate Port A pins as inputs.
4.8 8-Bit Timer Interrupt
This timer can create two types of interrupts. A timer overflow interrupt
will occur whenever the 8-bit timer rolls over from $FF to $00 and the
enable bit TOFE is set. A real time interrupt will occur whenever the
programmed time elapses and the enable bit RTIE is set. This interrupt
will vector to the interrupt service routine located at the address specified
by the contents of memory location $3FF8 and $3FF9.
4.9 16-Bit Timer1 Interrupt
There are five different timer interrupt flags that cause a 16-bit timer1
interrupt whenever they are set and enabled. The interrupt flags are in
the timer1 status register (TSR), and the enable bits are in the timer1
control register1 (TCR1). Any of these interrupts will vector to the same
interrupt service routine, located at the address specified by the contents
of memory location $3FF6 and $3FF7.
4.10 16-Bit Timer2 Interrupt
There are five different timer interrupt flags that cause a 16-bit timer2
interrupt whenever they are set and enabled. The interrupt flags are in
the timer2 status register (TSR), and the enable bits are in the timer2
control register1 (TCR1). Any of these interrupts will vector to the same