Table 32 - Interrupt Control Table
FIFO
MODE
ONLY
INTERRUPT
IDENTIFICATION
REGISTER
INTERRUPT SET AND RESET FUNCTIONS
PRIORITY
LEVEL
INTERRUPT
TYPE
INTERRUPT
SOURCE
INTERRUPT
RESET
CONTROL
BIT 3 BIT 2 BIT 1 BIT 0
0
0
0
1
0
1
1
0
-
None
None
-
Highest
Receiver Line
Status
Overrun Error,
Parity Error,
Reading the Line
Status Register
Framing Error or
Break Interrupt
0
1
1
1
0
0
0
0
Second
Second
Received Data
Available
Receiver Data
Available
Read Receiver
Buffer or the FIFO
drops below the
trigger level.
Character
Timeout
No Characters
Have Been
Reading the
Receiver Buffer
Indication
Removed From or Register
Input to the RCVR
FIFO during the
last 4 Char times
and there is at
least 1 char in it
during this time
0
0
0
0
1
0
0
0
Third
Transmitter
Holding Register Holding Register
Empty Empty
Transmitter
Reading the IIR
Register (if Source
of Interrupt) or
Writing the
Transmitter
Holding Register
Fourth
MODEM Status Clear to Send or
Reading the
Data Set Ready or MODEM Status
Ring Indicator or
Data Carrier
Detect
Register
75
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