Table 30 - Interrupt Control Table
FIFO
MODE
ONLY
INTERRUPT
IDENTIFICATION
REGISTER
INTERRUPT SET AND RESET FUNCTIONS
PRIORITY INTERRUPT
INTERRUPT
SOURCE
None
INTERRUPT
RESET CONTROL
BIT 3 BIT 2 BIT 1 BIT 0
LEVEL
TYPE
None
Receiver Line Overrun Error,
0
0
0
1
-
-
0
1
1
0
Highest
Second
Second
Reading the Line
Status Register
Status
Parity Error,
Framing Error or
Break Interrupt
0
1
1
1
0
0
0
0
Received
Data
Available
Receiver Data
Available
Read Receiver
Buffer or the FIFO
drops below the
trigger level.
Character
Timeout
No Characters
Have Been
Removed From
or Input to the
RCVR FIFO
Reading the
Receiver Buffer
Register
Indication
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
Transmitter
Holding Register Register (if Source
Empty
Reading the IIR
of Interrupt) or
Writing the
Transmitter Holding
Register
Fourth
MODEM
Status
Clear to Send or Reading the
Data Set Ready MODEM Status
or Ring Indicator Register
or Data Carrier
Detect
69
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