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HT82K28 Datasheet(PDF) 8 Page - Holtek Semiconductor Inc |
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HT82K28 Datasheet(HTML) 8 Page - Holtek Semiconductor Inc |
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8 / 20 page  HT82K28A 8 February 16, 2000 b4~b0 Typematic rate b4~b0 Typematic rate 00000 00001 00010 00011 00100 00101 00110 00111 01000 01001 01010 01011 01100 01101 01110 01111 30.0 26.7 24.0 21.8 20.0 18.5 17.1 16.0 15.0 13.3 12.0 10.9 10.0 9.2 8.6 8.0 10000 10001 10010 10011 10100 10101 10110 10111 11000 11001 11010 11011 11100 11101 11110 11111 7.5 6.7 6.0 5.5 5.0 4.6 4.3 4.0 3.7 3.3 3.0 2.7 2.5 2.3 2.1 2.0 · Default ¨ delay: 500ms± 20% ¨ typematic rate=10.9 characters/sec± 20% Commands to the system 00: keyboard detect a error/overrun (set 2, set 3) AB,83: keyboard ID AA: BAT completion FC: BAT failure EE: Echo FA: Acknowledge FE: Resend FF: Keyboard detects a overrun (set 1) · FA: Acknowledge If the KB (Keyboard) receives any valid input except EE (echo) and resend (FE) then send an FA to the system first. If the command is EE, then send an EE back to the system. If the command is FE, then send the last key code to system. If there is an interrupt while sending FA, the KB discards the FA and accepts the command from the system and processes it. · 00/FF: Key overrun If the keyboard detects an overrun error, the KB sends an overrun error code to the system. mode 1: FF mode 2,3: 00 · FE: Resend The KB issues an FE when there is a parity error in transmission. Data communications · Data output ¨ If CLK=0, no transmission (keyboard inhib- ited). ¨ If CLK=1, DATA=0, no transmission (sys- tem request to send). ¨ If CLK=1, DATA=1, transmission permit- ted. ¨ Data will be valid before the trailing edge and beyond the leading edge of the clock. ¨ The KB checks the clock line for an active level at least every 60ms. ¨ If line contention occurs (system brings the clock low before the tenth clock), set clock=data=high. · Data input ¨ The system overrides the clock line for at least 60ms ¨ The keyboard checks the state of the clock line at intervals of no more than 10ms ¨ If a system request-to-send is detected, the keyboard counts 11 data bits. ¨ Data will be valid before the rising edge and beyond the falling edge ¨ After the 10th bit, the keyboard checks for an active level on the "data" line. If the line is active it is forced to be inactive, and counts one more bit. Note: This action signals the system that the keyboard has received its data. Upon reception of this signal, the system returns to the ready state, in which it can accept keyboard outputs or goes to the inhibit state until it is ready. If the keyboard "data" line is found to be at an inactive level following the 10th bit, a frame error has occurred, and the keyboard contin- ues to count until the "data" line becomes ac- tive. The keyboard then makes the "data" line inactive and sends a Resend. |
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