Many modern system boards have both a 5 pin DIN and a Miniature 6 pin DIN connector as keyboard interface sockets. The IBM PS/2 range of computers introduced a smaller connector, a Miniature 6 pin DIN, and this PS/2 interface is becoming the new standard. The pins on the 5 pin DIN connector are assigned thus: ![]() Keyboard command for bullet point on pc Pc#Until recently, most PC computers used a 5 pin DIN connector on the computers system board and this supplied plus 5 volt and ground to the keyboard, and received data and clock signals from the keyboard, and supplied them to the keyboard interface circuit on the system board. The PC keyboard is connected to the computer via one of two types of connector. The key tops press down a capacitive plate close to two capacitive plates on the circuit board inside the keyboard, thus rising the capacitance between the X and Y lines of the matrix. Keyboard command for bullet point on pc series#The key matrix is a series of very tiny capacitors joining the X and Y lines of the matrix. The original IBM PC, PC/XT and PC/AT computers used this type of keyboard. These high quality keyboards were popular in the early days of PC computers but are very expensive to produce. Today this type of keyboard is available in both soft-touch and click type and is very reliable. The earliest examples had poor feel and were often quite unreliable. This type of keyboard has improved a lot over the years. The better quality keyboards have a life expetancy of one or two million key presses per key. These have a toggle action and usually provide good tactile and audible resposes. Three types of keyboard contacts (switches) have been used in PC keyboards In the past many computer systems have used ASCII codes to represent the keys in the matrix but the DOS computers use quite a complex procedure of Press and Release codes. Keyboard command for bullet point on pc code#When the keyboard processor finds a "Key Press" during its scanning of the matrix, it sends a code to represent that key, to a keyboard interface circuit in the computer. The keyboard processor uses a look-up table to find a code that represents the key that has been pressed. Later PC keyboards used 8049 processors, and the 101 key keyboard needs at least a 10 by 11 matrix to access all the keys. The matrix usually consisted of eight output lines and 11 or 12 input lines. The first PC keyboards used a 8048 processor chip and an 8 by 11 or 12 matrix. The input lines are pulled high by pull-up resistors, but will be pulled low if jointed to an active low output line by a key press. The keyboard processor puts an active low, "one of" count on each output line in turn, and then it scans the input lines, one at a time, for a low. ![]() ![]() The latest trend is to an Ergonomic Keyboard design like this one from Microsoft.Ī typical modern computer keyboard consists of processor chip connected to a matrix of keys arranged in an array of X and Y scan lines. There was also two extra function keys provided on this keyboard. This keyboard had the function keys along the top of the keyboard and a Numeric Keypad at the right hand end. The IBM AT introduced a 101 key keyboard and this soon became the standard for most PC clones. The keyboard was connected to the PC using a 5 pin DIN connector and this was plugged into a socket on the rear of the system board. The IBM PC was equipped with a keyboard that had 84 keys, with the function keys on the left side of the keyboard. ![]() The PC keyboard Phil Storrs PC Hardware book The PC Keyboard operation
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