Serial cable how many pins

For data signals, the "on" state occurs when the received signal voltage is more negative than -3 volts, while the "off" state occurs for voltages more positive than 3 volts. For control signals, the "on" state occurs when the received signal voltage is more positive than 3 volts, while the "off" state occurs for voltages more negative than -3 volts. To bring the signal to the "on" state, the controlling device unasserts or lowers the value for data pins and asserts or raises the value for control pins.

Conversely, to bring the signal to the "off" state, the controlling device asserts the value for data pins and unasserts the value for control pins.

The "on" and "off" states for a data signal and for a control signal are shown below. The Data Pins Most serial port devices support full-duplex communication meaning that they can send and receive data at the same time.

Therefore, separate pins are used for transmitting and receiving data. However, some types of serial port devices support only one-way or half-duplex communications. In this guide, it is assumed that a full-duplex serial port is connected to your device. The Control Pins 9-pin serial ports provide several control pins that:. The plugs contain sockets and pins, with each pin numbered and labeled. A serial pinout diagram is presented below. The RS protocol uses a 9 pin serial port that can have either male or female connectors.

The most recent version of the protocol is known as RSC. RSC retains the features of RS but uses 25 pins rather than a 9 pin serial pinout. Whether a DB9 serial pinout or a 25 pin connection is used, only three of the pins are required to connect terminal devices. Each pin in a 9 or 25 serial connector pinout has its own distinct function. You can also learn RS pinout. In addition to defining electrical characteristics, RS specifies the signals used in serial cable pinouts and serial ports.

Familiar items such as timing signals and ground are included in these specifications. Protective Ground -This signal is connected to the chassis ground of the metallic connector.

These signals are the primary RS signals, but the protocol allows for secondary signals as well. Using the RS protocol you can connect two computers that do not have modems by using a null modem cable. Other than that, it's just multiple serialised tasks at the same time.

Ramhound I understand that's the meaning of "serial", but then what are the other pins for? Dave Rook's last comments makes it clear. Show 5 more comments. Active Oldest Votes. The original serial had 3, 5 or even 7 pins, but only one to carry the data.

The three pins serial worked like this: The extra pin for a common ground is needed so that the other computer knows what to compare the data signal with. If you want you might call this two serial lines. You will notice two power lines, and one data pair basically one line with differential signaling PCIe has serial lanes. This has two reasons: Flexibility: It is easier to reconfigure mostly independent lanes Signal Skew.

Improve this answer. Hennes Hennes Nice answer, 2 questions 1. USB 3 has more pins. Does it have parallel "lanes" like PCI-e? Even 1-lane PCI-e has judging from images nearly 20 pins. Are these used for "sub-lanes"? I will add a table with PCIe x1 pinsout. You will discover that many of them are not data pins. Also, yes. USB3 uses multiple data paths. Ok, it's clear now.

BartvanHeukelom - Overhead doesn't exist in a situation like this. Each connection is seperate and does not effect one another unless designed to do so. Show 1 more comment. Shinrai Shinrai BartvanHeukelom - The number of pins is not the important difference between serial and parallel cables.

Its how the transmit and recieve lines were used and how the standard was designed serial data vs parallel data in theory you could design both with the same number of pins if you wanted. Add a comment. For completeness here's the RS DB25 pinout used in early PCs In my experience, most computers and serial devices only really used pins , 20, 22 at most. Here's a typical diagnostic breakout-box of that era:. I'm just wonder what the point of those "secondary" pins were. Higher reliability?