EKK8301 Ver la hoja de datos (PDF) - ELAN Microelectronics

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EKK8301

Keyboard Encoder

ELAN Microelectronics 

eKK8301

Keyboard Encoder

6 Function Descriptions

6.1 Keyboard Buffer

The keyboard will buffer 16 bytes in a first-in first-out order when the system is able to

receive scan codes from the keyboard. The response codes and repeated codes will

not be buffered. If keystrokes generate a multiple-byte sequence, the entire

sequence must fit into the buffer or the keystroke is discarded and a buffer-overrun

condition occurs.

6.2 Power-on Reset and Self Test

The duration of the keyboard Power-on Reset(POR) should be within 150

milliseconds and 2 seconds after the power is applied to the keyboard.

After executing POR, the keyboard executes a self test. The LEDs are turned on at

the beginning and off at the end of the self test. The self test takes a minimum 300

milliseconds and a maximum 500 milliseconds. If the self test is successful, a

completion code AA hex is sent to the system and the keyboard starts scanning. If

the self test fails, and error code is sent, the keyboard is disabled and waits for a

command from the system. The completion codes are sent between 450

milliseconds and 2.5 seconds after POR, and between 300 and 500 milliseconds after

a RESET command is acknowledged.

6.3 Keyboard Data Output

When the keyboard is ready to send data to the system, it first checks clock and data

lines. If either one is in the low state, data is stored in the keyboard buffer. If both

are in the high state, keyboard starts clocking data out. Data will be valid before the

trailing edge and after the leading edge of the clock pulse. During the transmission

the keyboard checks the clock line at least every 60 microseconds. If the system

lowers the clock lines before the leading edge of the 10th clock, the keyboard should

stop sending, then buffer the data and return clock and data lines to high state.

6.4 Keyboard Data Input

When the system is ready to send data to the keyboard, if first checks clock line to

see if keyboard is sending data. If keyboard is not sending data or it is sending data

but has not reached the 10th clock, the system can inhibit the interface by forcing the

clock line low for more than 60 microseconds and prepares to send data. The

keyboard checks clock line status at least every 5 milliseconds. If a system Request

to Send(RTS) is detected, the keyboard clocks 11 bits in. After the 10th bit, the

keyboard checks for a high state in data line then pulls it low and clocks one more bit

to signal the system that data has been received. If data is low after the 10th bit, it

indicates a frame error. The keyboard should continue to count until data line goes

high, then pulls it low and issues a RESEND to the system.

4•

Product Specification (V1.0) 08.07.2002

(This specification is subject to change without further notice)

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