Sun Microsystems Netra T4 AC100, Руководство по обслуживанию и системе

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Chapter 10 Functional Description 10-29
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.
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
2
) is
anything greater than +3 VDC and a binary 0 (000
2
) is anything less than –3 VDC.
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 to +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
system default is set to RS-232.
Note –
The serial port protocol is changed using the OBP, not by changing a jumper
setting.
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 one percent for any rate that is generated between
50 Kbaud and 256 Kbaud.
Asynchronous Rates
The serial asynchronous ports support twenty baud rates that are all exact divisors
of the crystal frequency (with the exception of 110, which is off by less than one
percent). Baud rates are 50, 75, 110, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200,
38400, 57600, 76800, 115200, 153600, 230400, 307200, and 460800.