Hardware Reference
In-Depth Information
Serialportswereonceusedtoconnectprintersandexternalmodems,butinmodernHome
Theater PCs they are used to connect infrared transceivers to allow for remote control op-
eration.
The official specification recommends a maximum cable length of 50 feet. The limiting
factor is the total load capacitance ofcable and input circuits ofthe interface. The maxim-
um capacitance is specified as 2,500pF (picofarads). Special low-capacitance cables can
effectively increase the maximum cable length greatly, to as much as 500 feet or more.
Also available are line drivers (amplifier/repeaters) that can extend cable length even fur-
ther.
Tables 14.11 , 14.12 , and 14.13 show the pinouts of the 9-pin serial connector, the 25-pin
serial connector, and the 9-pin-to-25-pin serial adapter, respectively.
Table 14.11 Pinout for a 9-Pin Serial Port Connector
Table 14.12 Pinout for a 25-Pin Serial Port Connector
 
 
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