Eia Levels; Synchronous Rates; Asynchronous Rates; Slew Rate And Cable Length - Sun Microsystems Ultra 80 Service Manual

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
per second.
C.1.10.3

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 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. Switching from RS-232 to RS-423
protocol is accomplished by changing jumpers J2604 and J2605. Jumper positions 1
and 2 are for RS-232 and jumper positions 2 and 3 are for RS-423.
The preferred signaling protocol is RS-423. The higher voltages of R-232 make it
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.
C.1.10.4

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.
C.1.10.5

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 1
percent). Baud rates include 50, 75, 110, 200, 300, 600, 1200, 1800, 2400, 4800, 9600,
19200, 38400, 57600, 76800, 115200, 153600, 230400, 307200, and 460800.
C.1.10.6

Slew Rate and Cable Length

The maximum RS-423 cable length is 118 feet (30 meters) and the maximum RS-232
cable length is 50 feet (15.24 meters). The slew rate changes depending on the speed.
For speeds less than 100 Kbaud, the slew rate is set at 5 VDC per microsecond. For
) is anything less than -3 VDC.
2
Appendix
) is
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