The previous section presupposes knowledge of the correspondence between terminal signals and serial port pins. Here's a reference for that correspondence, taken from David Tal's <GSRGAAO@TECHNION.BITNET> ``Frequently Used Cables and Connectors'' document. I'm including a diagram illustrating the connectors, and a table listing the correspondence between pin numbers and terminal line signals.
DB-25 DB-9 Name EIA CCITT DTE-DCE Description
Pin # Pin #
1 13 1 5 _______________________________ _______________ \ . . . . . . . . . . . . . / \ . . . . . / RS232-connectors \ . . . . . . . . . . . . / \ . . . . / seen from outside --------------------------- ----------- of computer. 14 25 6 9 DTE : Data Terminal Equipment (i.e. computer) DCE : Data Communications Equipment (i.e. modem) RxD : Data received; 1 is transmitted "low", 0 as "high" TxD : Data sent; 1 is transmitted "low", 0 as "high" DTR : DTE announces that it is powered up and ready to communicate DSR : DCE announces that it is ready to communicate; low=modem hangup RTS : DTE asks DCE for permission to send data CTS : DCE agrees on RTS RI : DCE signals the DTE that an establishment of a connection is attempted DCD : DCE announces that a connection is established
Next Chapter, Previous Chapter
Table of contents of this chapter, General table of contents
Top of the document, Beginning of this Chapter