Serial Port Functions; Eia Levels; Synchronous Rates - Sun Microsystems Sun Blade 1000 Service Manual

Note – Interrupts are generated when the buffer reaches 32 bytes or half full.
The line drivers and line receivers are compatible with both RS-232 and RS-423
protocols. Software control sets the line drivers and line receivers to either RS-232 or
RS-423 protocols. The line driver slew rate is also programmable. For baud rates
over 100 Kbaud, the slew rate is set to 10 VDC/µsec. For baud rates under 100
Kbaud, the slew rate is set to 5 VDC/µsec.
C.1.13.2

Serial Port Functions

Modem connection to the serial port allows access to the Internet. Synchronous X.25
modems are used for telecommunications in Europe. An ASCII text window is
accessible through the serial port on your workstation. Low speed printers,
buttonboxes (for CAD/CAM applications), and devices that function like a mouse
are also accessible through the serial port. The additional speed of the serial port can
be used to execute communications with a CSU/DSU for a partial T1 line to the
Internet at 384 Kbaud.
C.1.13.3

EIA Levels

Each serial port supports both RS-232 and RS-423 protocols. RS-232 signaling levels
are between -3 VDC and -15 VDC and +3 VDC and +15 VDC. A binary 1 (001
anything greater than +3 VDC and a binary 0 (000
The signal is undefined in the transition area between -3 VDC and +3 VDC. The line
driver switches at -10 VDC and +10 VDC with a maximum of -12 VDC and +12 VDC
in RS-232 mode. RS-423 support is similar except that signaling levels are between -
4 VDC to -6 VDC and +4 VDC and +6 VDC. The line driver switches at -5.3 VDC
and +5.3 VDC with a maximum of -6 V and +6 VDC.
The preferred signaling protocol is RS-423. The higher voltages of RS-232 makes it
more difficult to switch at the higher baud rates. The maximum rate for RS-232 is
approximately 64 Kbaud while the maximum rate for RS-423 is 460.8 Kbaud. The
workstation default is set to RS-232.
C.1.13.4

Synchronous Rates

The serial synchronous ports operate at any rate from 50 Kbaud to 256 Kbaud when
the clock is generated from the serial port controller. When the clock is generated
from an external source, the synchronous ports operate at up to 384 Kbaud. Clock
generation is accurate within 1 percent for any rate that is generated between 50
Kbaud and 256 Kbaud.
) is anything less than -3 VDC.
2
Appendix C Functional Description
) is
2
C-35