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3
.
2
Interrupt Configuration
Interrupt requests may originate from eight sources
on the
SIB.
Four
interrupts can
be
generated
by the CTC when any
one
of the
USAFTs
is
ready
to
accept
a
data character
(TxRDY)
.
The order
of
priority
is
channel
first, through
channel
3.
Another
four interrupts can be
generated when any
one of the USARTs
contains
a
character that
is
ready
to be
input
to the
CPU
(RxRDY)
.
Again,
the
order
of
priority
is
channel
first, through
channel
3,
However, the RxRDY lines
will have
priority
over any of the
TxRDY
lines.
Each
interrupt
is
maskable under program control.
Figure 3.2.1
indicates
the
priority order between
the two
daisy-chained
CTC
's.
<IEI
lEO
RR
-
RECEIVER
READY
TR- TRANSMIT
READY
^
lEO
FIGURE
3.2.1
SIB
INTERRUPT PRIORITY
STRUCTURE
6
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