12
Fastcom
®
: G232/8-PCI-335
MAXIMUM DATA RATE
Due to the nature of RS-232 communications, attainable baud rates tend to vary greatly. The ability to achieve
higher baud rates depend on many factors including the interrupt handling ability of target machine, environment
noise and especially cable lengths.
In order to make cable length determination easier, we have developed an equation based on an interpolation of
recorded laboratory data. By measuring the maximum attainable baud rates at varying cable lengths and plotting
the data, we were able to create a linear approximation of the data set.
Please use the equation below to determine approximate correlations between maximum baud rate and cable
length up to a typical maximum of 2,062,500 bps (rates above 1 Mbps are possible but not guaranteed).
To determine the max length at a given baud use:
d = ( -9.04*10
-5
* bps ) + 192
To determine the max baud at a given cable length use:
bps = ( -11,000 * d ) + (2.13*10
6
)
d = approximate MAX cable length in feet
bps = estimated MAX baud rate in bits per second
Equations are based on experiments using Olympic cable number 2829 with 30pf/ft nominal capacitance at a
maximum of 83 ft (CL not to exceed 2500 Pico farads per EIA-232). These equations are an estimate of the
maximum capabilities in the user’s environments; different cable capacitance will yield different results. These
equations are only valid when using a Fastcom: G232/8-PCI-335
adapter, they cannot be utilized when dealing
with other Fastcom boards.