TABLE 34 - INTERRUPT CONTROL
FIFO
MODE
ONLY
INTERRUPT
IDENTIFICATION
REGISTER
INTERRUPT SET AND RESET FUNCTIONS
PRIORITY INTERRUPT
INTERRUPT
SOURCE
INTERRUPT
RESET
BIT 3
BIT 2 BIT 1 BIT 0
LEVEL
TYPE
CONTROL
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 Receiver Data
Read Receiver
Buffer or the FIFO
drops below the
trigger level.
Available
Available
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 Empty Empty
Transmitter
Holding Register
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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