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HT82K28 数据表(PDF) 4 Page - Holtek Semiconductor Inc |
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HT82K28 数据表(HTML) 4 Page - Holtek Semiconductor Inc |
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4 / 20 page  HT82K28A 4 February 16, 2000 Functional Description The HT82K28A basic function is to detect key press and release activity and to transmit the corresponding scan code, as well as make and break codes to the system. The device also accepts commands from the sys- tem and responds to the system if necessary. All communication between the keyboard and the system is managed through the CLOCK and DATA pins. The keyboard begins to scan for pressed or re- leased keys and commands from the system after the BAT (Basic Assurance Test) has been run. Working modes Three working modes are supported by the HT82K28A. These are setup by the alternate scan code command F0. The various modes are described as follows. Mode 1 · Supports code set 1 for PS/2 model 30 key- boards. · Enters mode1 after an F0 Command is issued followed by a 1". · Contains an 11 bit data stream, including one start bit (always zero) eight data bits, one par- ity bit (odd parity) and one stop bit (always one). · All keys are typematic/make/break as default. · The working mode can be changed again in this mode, by issuing an F0 command fol- lowed by an option. See the F0 command for more detail. Mode 2 · Supports code set 2 for PC/AT, PS/2 model 50, 60 keyboards. · Enters mode 2 after power on. The working mode can be changed by an F0 command followed by an option byte 1, 2 or 3. See the F0 command for more details. · Contains an 11 bit data stream, including one start bit (always zero) eight data bits, one par- ity bit (odd parity) and one stop bit (always one) · All keys are typematic/make/break as default. Mode 3 · Supports code set 3, for PS/2 model 80 key- boards. · Enters mode 3 when an F0 command is issued followed by a 3". · Contains an 11 bit data stream, including one start bit (always zero) eight data bits, one par- ity bit (odd parity) and one stop bit (always one). Buffers The buffers support the following functions: · 16-byte FIFO buffer: stores 16 keystrokes scan codes. · Additional keystrokes will be ignored. · Response codes, i.e FA/FE... do not occupy buffer positions. Basic assurance test - BAT The following functions are offered by the Basic Assurance Test: · Turns on LED status indicators. · Keyboard processor test. · RAM test. · Turns off LED status indicators, i.e. the LEDs. · Reports the BAT result to the system. Note: During the BAT, activity on the "clock" and "data" line are ignored. The LED¢s are turned on at the beginning and turned off at the end of the BAT. The BAT takes a minimum of 450ms after POR and a maximum of 2.5s. The re- sponse to a satisfactory BAT completion is ²AA² and response to BAT failure is an ²FC² error. The reset keyboard com- mand ²FF² will also cause the keyboard to execute the BAT. Completion codes are sent between 300 and 500ms after a reset command is acknowledged. After the BAT, the keyboard sets the keys to typematic and make/break, and sets the default typematic rate and delay. |
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