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EKK8301 Datasheet(PDF) 8 Page - ELAN Microelectronics Corp |
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EKK8301 Datasheet(HTML) 8 Page - ELAN Microelectronics Corp |
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8 / 30 page  eKK8301 Keyboard Encoder 4 • Product Specification (V1.0) 08.07.2002 (This specification is subject to change without further notice) 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 10 th 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 10 th 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 10 th 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 10 th 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. |
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