------------- NOTE WELL!!!! Common PC Connectors Seen from the Back of the PC These pinouts are looking into the connector from the outside, and that soldering the soldercup-types and using insertable pins and sockets from the inner side is also again backwards of the views shown below!!! Even so, these are always marked on both sides if you have good vision or use a magnifier or magnifier glasses. Often it is the numbers, sometimes just a mark ridge between pins 1 and 2. But you CAN see it. I have never seen one without some identifier. Also do not mistake a male for a female. The one that fits within the outer "D" shroud of the other is FEMALE!!! This is why they use the designators DB9P and DB9S and DB25P and DB25S! The letters DB are the connector type, odd number of total pins, rows offset. P means Pins and S means Sockets!! ---------------------------------------------------------------------- Video Connectors on Rear Panel of Computer The common connector for all types of video output is the DB9S. It is the typical "D" connector, so-called because one row of sockets whose number is always even has beside it another row whose number is odd and staggered. Depending on whether the monitor and driver card are for CGA, or Color Graphics Adapter, or for Monochrome Text or MonoGraphics/Hercules, the pinout of signals varies slightly: --------------------------------- | Pin | CGA Mono | 9-pin Socket-type |-----|-------------------------| Video DE-9S | 1 | ground | | 2 | ground | 5 4 3 2 1 | 3 | red not used | \---------------------/ | 4 | green not used | holes -> \ O O O O O / | 5 | blue not used | \ O O O O / | 6 | intensity | \---------------/ | 7 | not used mono video | 9 8 7 6 | 8 | horizontal | | 9 | vertical | --------------------------------- ----------------------------------------------------------------------- RS232C Serial Ports The pinout of the IBM standard RS232C Serial Port is in two forms: The "XT" and the "AT" style connector, both of which may be found on either model depending on the card installed. The "XT" style is implemented with a DB25P connector with 13 pins top row and 12 pins bottom and staggered to resemble a flattened "D" with 25 pins. The "AT" style is simply a DB9P version of the DB25P with only the all important 9 pins used. Pinout follows later. XMT RCV RTS CTS DSR GND DCD -------------------------------------------------------- \ 1 2 3 4 5 6 7 8 9 10 11 12 13 / "XT" \ / pins --> \ 14 15 16 17 18 19 20 21 22 23 24 25 / ------------------------------------------------ DTR RI DTE LABELS (Data Terminal Equipment: Terminals, Computers, etc) (DCE Data Communications Equipment reverses XMT-RCV, RTS-CTS, DTR-DSR) (Used on Modems, and such as need transmit CDC and RI) DCD RCV XMT DTR GND ----------------------- \ 1 2 3 4 5 / "AT" DE-9P connector \ / pins --> \ 6 7 8 9 / --------------- DSR RTS CTS RI IMPORTANT PINS "XT" Pins 2 3 4 5 6 20 7 8 22 "AT" Pins 3 2 7 8 6 4 5 1 9 DTE LABEL XMT RCV RTS CTS DSR DTR GND DCD RI DCE LABEL RCV XMT CTS RTS DTR DSR GND DCD RI "Male" pins are used on the computer itself in the IBM family design to denote an interface which cannot be shorted and damage itself, no matter how one may try, even by stripping all wires in their cable and twisting them all together bare! This is because the driver chips for this port are current limited and cannot overcurrent and thus overheat. Communications are signaled using +/-12 Volt serial pulses and handshake lines which indicate readiness to transmit or receive and an enabled state or disabled state are active high voltage wise, or active low before conversion to RS-232C. Inactive data line is low or just "mark"ing time, with its value logically a 1. Start bit is a high bit.
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