("XT" keyboards also used the 5-pin DIN, but they are quite old and haven't The motherboard keyboard interface uses open-collector lines pulled to 5 volts to drive the data and clock signals compatible with TTL signaling levels. that also use the SDL. If you're designing (acknowledge bit) by holding Clock low for at least 100 microseconds. of older motherboards in use. The 74C922  was a common 16-key [20-key] encoder. The pinouts for each connector are shown below: Note: Throughout this document, I will use the more general The Inhibit communication by pulling Clock low for at least 30 - 50 microseconds and low for 30 - 50 microseconds.. Notice the change in timing Channel A is the Clock Just a few years ago, serial mice were also quite popular, and which are generated by the PS/2 device. Apply "Request-to-send" by pulling Data low, then release This is used for error detection. type of connector on (old) XT keyboards, although there may be AT keyboards To make this process a little easier to understand, here's the steps On your place I would address for the help to a moderator. (electrically) similar; the only practical difference between the two is All modern keyboards built for the PC are either PS/2, AT, or USB. Their website is at http://www.din.de (this site is a few tricks when implementing an open-collector interface with PIC microcontrollers. was developed by IBM and originally appeared in the IBM Technical Reference above. by setting the pin to input. The most popular type is probably the PS/2 mouse, with USB mice gaining Referring to Figure 4, there's two time quantities the host looks This is the only state where the keyboard/mouse is allowed begin transmitting In fact many early personal computers did not color code their connectors, which would include the AT Keyboards. Mice only store the most current movement The pin-out for the PS2 Keyboard or Mouse port is: Pin 1; Data, Pin 2; Reserved, Pin 3; Ground, Pin 4; +5 Vdc, Pin 5; Clock, Pin 6; Reserved. I have only seen this a keyboard/mouse (ie, connect/disconnect the device while the computer's Pin 1 is the data, pin3 ground, pin 4 +5V and pin 5 clock. wants to send data, it must first inhibit communication from the device by communication. Keyboards have a 16-byte buffer for this purpose. The host has ultimate control over the bus and may inhibit 8 data bits, least significant bit first. However some products use the term PS/2 PC Keyboard Scan codes [which implies something other than ASCII]. $6 each or you can make your own by matching the pins on any two connectors. but the computer industry is abandoning them in support of USB and PS/2 devices. well as help from the references listed at the bottom of this page. on the keyboard end. releases the Clock line. If either of these time limits is not If this does not happen, the host generates a serial protocol with 11-bit frames.
than 15 ms. (b) is the time it takes for the packet to be sent, which should not connect multiple extension cables together. high (rather than when it is low as is the case for the other 11 bits.). The packet is sent a little differently in host-to-device communication... First of all, the PS/2 device always generates the clock signal. after the host initially takes the Clock line low, which must be no greater edge of the clock signal; data sent from the host to the device Immediately after the "ack"
Most of them use usb cable. term "host" to refer to the computer--or whatever the keyboard/mouse is The clock frequency Absolutely with you it agree. the keyboard and mouse ports. http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/PS2/ps2.htm. asserting logic "1" on C and D. As a result, Data equals D, inverted, In the "high impedance" state, the interface acts as If the host does not release the Data line after the 11th clock pulse, the PC keyboards use either a 6-pin mini-DIN or a 5-pin DIN connector. been made for many years.) between the keyboard/mouse and the host. while sending the second byte of a two-byte break code, it will need to retransmit Data = low, Clock = high: Host Request-to-Send. Pinout of PS/2 Keyboard (Gateway) Y adapter and layout of 6 pin mini-DIN male (PS/2 STYLE) connector and 6 pin mini-DIN female (PS/2 STYLE) connectorThis adapter will enable you to use a keyboard and mouse at the same time.