Serial Port - Sun Microsystems Ultra 80 Service Manual

Parallel Port Cables
The parallel port cable is IEEE1284 compliant and consists of 18 pairs of signal wires
that are double shielded with braid and foil. The maximum length of the parallel
port cable is 2.2 yards (2 meters).
Electrical Characteristics
Drivers operate at a nominal 5-VDC transistor-transistor logic (TTL) levels. The
maximum open circuit voltage is 5.5 VDC and the minimum is -0.5 VDC. A logic
high-level signal is at least 2.4 VDC at a source current of 0.32 mA and a logic
low-level signal is no more than 0.4 VDC at a sink current of 14 mA.
Receivers also operate at nominal 5-VDC TTL levels and can withstand peak voltage
transients between -2 VDC and 7 VDC without damage or improper operation. The
high-level threshold is less than or equal to 2.0 VDC and the low-level threshold is at
least 0.8 VDC. Sink current is less than or equal to 0.32 mA at 2.0 VDC and source
current is less than or equal to 12 mA at 0.8 VDC.
C.1.10

Serial Port

The system incorporates two serial ports. Each serial port is synchronous and
asynchronous with full modem controls. All serial port functions are controlled by a
serial port controller that is electrically connected to the system through the EBus.
Line drivers and line receivers control the serial port signal levels and provide
RS-232 and RS-423 compatibility. Each serial port interfaces through its own DB-25
connector.
The major features of each serial port include:
Two fully functional synchronous and asynchronous serial ports
DB-25 connectors
Increased baud rate speed (to 384 Kbaud, synchronous, 460.8 Kbaud,
asynchronous)
Variable edge rate for greater performance
EBus interface
The following figure shows a functional block diagram of the serial port:
Appendix -23