Technical data

Firmware Description

USB and PS/2 Multimedia Keyboard Interface, Rev. 1

Freescale Semiconductor 15

6. Device reads the Clock line and aborts communication if the Clock line is low.

7. Repeat steps 4 to 6 for Data 0 to Data 7, the parity bit and the stop bit.

8. Device releases the Clock line high.

CLOCK

DATA

START DATA0 DATA1 DATA2 DATA3 DATA4 DATA5 DATA6 DATA7 PARITY STOP

STEP 1,2

5,6

Figure 1-10. Device to Host Communication

KBD_OUT is the routine for transmitting data to the host. The data to be transmitted is put into V_TxByte

before calling this routine.

1.5.6 PS/2 Keyboard Command

Both the host and the keyboard may send commands to each other. The keyboard transmits an

acknowledge ($FA) after receiving a valid command. When the keyboard receives an invalid command,

it returns a resent command ($FA).

1.5.7 Host to Keyboard Commands

Table 1-2. Host to Keyboard Commands

Code Description Implemented

$ED Set status indicators YES

$EE Echo YES

$F0 Set alternate Scan Code NO

$F2 Get keyboard ID YES

$F3 Set typematic repeat rate YES

$F4 Enable Scan YES

$F5 Disable Scan YES

$F6 Set default values YES

$F7 Set all keys typematic NO

$F8 Set all keys make/break NO

$F9 Set all keys make NO

$FA Set key type typematic/make/break NO

$FB Set key type typematic NO

$FC Set key type make/break NO

$FD Set key type make NO

$FE Resent the last command YES

$FF Reset YES