Updated

OperatingSystem/monitor_v2/include/vt82c42.s

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+;----------------------------------------------------------------
+;Keyboard interface driver for Z8C 
+;Controller used: vt82c42
+;Datasheet: http://www.s100computers.com/My%20System%20Pages/MSDOS%20Board/vt82c42%20PC%20Keyboard%20conrtroller.pdf
+;by Dennis Gunia (04/2022)
+;----------------------------------------------------------------
+
+;IO Ports
+CS_VT82C42_DATA .EQU F0h
+CS_VT82C42_CTRL .EQU F1h
+
+keyboard_init_io:   ;Subroutine for initializing keyboard controller
+    LD A, A7h                   ;Disable Mouse
+    OUT (CS_VT82C42_CTRL), A
+    LD A, ADh                   ;Disable Keyboard
+    OUT (CS_VT82C42_CTRL), A
+_keyboard_init_flush_buffer:
+    IN A,(CS_VT82C42_DATA)      ;Read buffer
+    IN A,(CS_VT82C42_CTRL)      ;Read status byte
+    BIT 0,A                     ;Test if buffer is empty
+    JR Z, _keyboard_init_flush_buffer
+    ;buffer is now flushed. Now set the Controller Configuration Byte 
+    IN A,(CS_VT82C42_CTRL)      ;Disable bits 0,1,6 (disablee IRQ and Translation)
+    AND 10111100
+    OUT (CS_VT82C42_CTRL),A
+    ;Perform Controller Self Test 
+    LD A, AAh
+    OUT (CS_VT82C42_CTRL), A
+    NOP
+    IN A,(CS_VT82C42_CTRL)  ;Check results
+    CP 55h
+    JR NZ, keyboard_init_failed
+    ;Perform Interface Tests 
+    LD A, ABh
+    OUT (CS_VT82C42_CTRL), A
+    NOP
+    IN A,(CS_VT82C42_CTRL)  ;Check results
+    CP 00h
+    JR NZ, _keyboard_init_failed
+    ;Enable Devices
+    LD A,AEh
+    OUT (CS_VT82C42_CTRL), A
+    ;Reset Devices 
+    LD A,FFh
+    OUT (CS_VT82C42_DATA), A    ;Send reset to keboard (0xFF command)
+    NOP
+    IN A,(CS_VT82C42_CTRL)      ;Read status byte
+    BIT 0,A                     ;Test if buffer is empty -> no keyboard found
+    JP NZ, _keyboard_init_dev_missing
+    CP A, 0xFC
+    JR Z, _keyboard_init_okay    ; 0xFC -> Success. Init done!
+    ;Else device error
+    LD HL, [STR_keyboard_init_failed]
+    CALL print_str
+    HALT
+_keyboard_init_failed:
+    LD HL, [STR_keyboard_init_err]
+    CALL print_str
+    HALT
+_keyboard_init_dev_missing:
+    LD HL, [STR_keyboard_init_missing]
+    CALL print_str
+    HALT
+_keyboard_init_okay:
+    LD HL, [STR_keyboard_init_okay]
+    CALL print_str
+    RET
+
+;Keyboard IO functions
+keyboard_read:
+    IN A,(CS_VT82C42_CTRL)      ;Read status byte
+    BIT 0,A                     ;Test if buffer is empty
+    RET NZ                      ;Return if empty
+    IN A,(CS_VT82C42_DATA)
+    RET                         ;Return with data in A
+
+keyboard_write:
+    PUSH AF
+_keyboard_write_wait:
+    IN A,(CS_VT82C42_CTRL)      ;Read status byte
+    BIT 1,A                     ;Test if buffer is full
+    JR Z, _keyboard_write_wait   ;Wait if input buffer is full
+    POP AF
+    OUT (CS_VT82C42_DATA), A
+    RET
+    
+
+;Status message strings
+STR_keyboard_init_okay:
+    .BYTE "PS/2 Keyboard initialized.",0
+STR_keyboard_init_err:
+    .BYTE "PS/2 Controller error! System HALT!",0
+STR_keyboard_init_failed:
+    .BYTE "PS/2 Keyboard error! System HALT!",0
+STR_keyboard_init_missing:
+    .BYTE "PS/2 no keyboard found!",0