IBM 5150 Hardware Reference Manual page 159

Table 24.
Interrupt Control Functions
Interrupt I D
Register Interrupt Set and Reset Functions
Bit 2 Bit 1
Bit 0
0 0 1
1 1 0
1
0
0
0 1 0
0
0
0
Priority
Level
-
Highest
Second
Third
Fourth
Interrupt
Type
None
Receiver
Line Status
Received
Data Avail­
able
Transmitter
Holding Reg­
ister Empty
MODEM Status
Interrupt Interrupt
Source
Reset Control
None
­
Overrun Error
or
Parity Error Reading the
or
Line Status
Framing Error
Register
or
Break Interrupt
Receiver
Reading the
Data Avail- Receiver
able
Buffer
Register
Reading the
II R Register
Transmitter (if source of
Holding Reg-
interrupt)
ister Empty or
Writing into
the Trans­
mitter Hold­
ing Register
Clear to Send
or
Data Set Ready
or
Reading the
Ring Indicator
MODEM Status
or Register
Received Line
Si gna I 0 etect
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