IBM RT Series Hardware Reference Manual page 79

Interrupt
ID Interrupt Set and Reset Functions
Register
Bit Bit Bit Priority Interrupt Interrupt Interrupt
2 1 0 Level Type Source Reset Control
0 0 1
-
None None
-
1 1 0 Highest Receiver Overrun Error or Reading the Line
Line
Parity Error or Status Register
Status Framing Error or
Break Intrpt.
1 0 0 Second Received Receiver Data Reading the Receiver
Data Available Buffer Register
Available
0 1 0 Third Transmitter Transmitter Holding Reading the IIR
Holding
Register Empty Register or Writing
Register into the Transmitter
Empty Holding Register
0 0 0 Fourth
Modem Clear to Send or Data
Reading the Modem
Status Set Ready or Ring Status Register
Indicator or Received
Line Signal Detect
Figure 13. Interrupt Control Functions
5080 Peripheral Adapter 23