24 lines
1016 B
Plaintext
24 lines
1016 B
Plaintext
;;********************************************************************************
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;; @module keyboard
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;; @type drive
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;; @details:
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;; Support for a PS2 Keyboard using the shift register of a 6522 VIA
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;; Pressing a key causes 11 bits to be sent: 1 start - 8 keycode - 1 parity - 1 stop
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;; The VIA is set up to interrupt after 8 bits have been shifted into the shift register
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;; from the external clock pulses of the keyboard (additional hardware required to
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;; address the hardware bug of the VIA, where bit get lost when the external clock
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;; transition happens during falling edge of PHI2). After reading the shift register,
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;; the VIAs T2 timer is set to interrupt after the last 3 bits have been shifted in,
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;; which takes about ~230ms.
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;;********************************************************************************
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.ifndef INCLUDE_KEYBOARD
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INCLUDE_KEYBOARD = 1
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.include "system.h65"
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.scope kb
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Import kb,init,irq_shift_reg_handler,irq_timer_handler,keycode,key_read
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KB_IO = IO1
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.endscope
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.endif
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