MicroBlaze Development Kit Spartan-3E 1600 Edition User Guide 65UG257 (v1.1) December 5, 2007 www.xilinx.comKeyboardRSome keys, called extended keys, send an “E0” ahead of the scan code and furthermore,they might send more than one scan code. When an extended key is released, an “E0 F0”key-up code is sent, followed by the scan code.The host can also send commands and data to the keyboard. Table 8-3 provides a short listof some often-used commands.The keyboard sends commands or data to the host only when both the data and clock linesare High, the Idle state.Because the host is the bus master, the keyboard checks whether the host is sending databefore driving the bus. The clock line can be used as a clear to send signal. If the host pullsthe clock line Low, the keyboard must not send any data until the clock is released.Figure 8-3: PS/2 Keyboard Scan CodesESC76` ~0ETA B0DCaps Lock58Shift12Ctrl141 !162 @1E3 #264 $255 %2EQ15W1DE24R2DT2CA1CS1BD23F2BG34Z1ZX22C21V2AB326 ^367 &3D8 *3E9 (460 )45- _4E= +55Back Space66Y35U3CI43O44P4D[ {54] }5B\ |5DH33J3BK42L4B; :4C' "52Enter5AN31M3A, <41> .49/ ?4AShift59Alt11Space29AltE0 11CtrlE0 14F105F206F304F40CF503F60BF783F80AF901F1009F1178F1207 E0 75E0 74E0 6BE0 72UG257_08_03_060506Table 8-3: Common PS/2 Keyboard CommandsCommand DescriptionED Turn on/off Num Lock, Caps Lock, and Scroll Lock LEDs. The keyboardacknowledges receipt of an “ED” command by replying with an “FA”, afterwhich the host sends another byte to set LED status. The bit positions for thekeyboard LEDs are shown below. Write a ‘1’ to the specific bit to illuminate theassociated keyboard LED.EE Echo. Upon receiving an echo command, the keyboard replies with the same scancode “EE”.F3 Set scan code repeat rate. The keyboard acknowledges receipt of an “F3” byreturning an “FA”, after which the host sends a second byte to set the repeat rate.FE Resend. Upon receiving a resend command, the keyboard resends the last scancode sent.FF Reset. Resets the keyboard.7 6 5 4 3 2 1 0Ignored CapsLockNumLockScrollLock
