AT&T 3B2/300 Technical Reference Manual page 389

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
Dual Universal Asynchronous Receiver/Transmitter.
The CONSOLE (UART 0) and CONTTY
(UART 1) are driven by a Signetics 2681-40 DUART. Each channel (0 and 1) provides the following
signals:
• Transmit data (TXD)
• Receive data (RXD)
• Data Carrier Detect (DCD)
• Data Terminal Ready (DTR).
Electrically, the DUART is on the peripheral bus with five other devices in the OMA Subsystem.
The UART has three output ports that are used for non-UART functions. These functions are listed
below:
• Control of off-board AC power relay via Output Port 2 (OP2) (PWRON[O]). The signal is high
during normal operations.
• Control of the Power indicator under certain operational conditions via Output Port 3 (OP3)
(GLEDON[l]).
• Output Port 4 (OP4) (UFEJCT[O]) is buffered and is sent to the floppy disk interface connector for
feature application.
• Output Port 5 (OPS) (UFDSEL[O]) is buffered and sent to JlO as the Floppy Drive Select
(FDSEL[O]).
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