IBM RT Series Hardware Reference Manual page 73

available, transmitter holding register empty, or modem status. The Interrupt signal is reset low on
the appropriate interrupt service or a master reset operation.
Note: Generates interrupt request.
Serial Output (SOUT), Pin 11: Composite serial data output to the communications link
(peripheral, modem or data set). The SOUT signal is set to the marking (logic 1) state on a master
reset operation.
Note: Provides data to attached device.
Input/Output Signals
Data Bus (07-00),
Pins
1-8: This bus consists of eight tri-state I/O lines. The bus provides
bidirectional communications between the NS16450 and the processor. Data, control words, and
status information are transferred through the D7-DO data bus.
External Clock Input/Output (XT ALl, XT AL2), Pins 16 and 17: These two pins connect the main
timing reference (crystal or signal clock) to the NS 16450.
5080 Peripheral Adapter 17