mirror of https://github.com/cc65/cc65.git
136 lines
3.4 KiB
ArmAsm
136 lines
3.4 KiB
ArmAsm
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; IJK joystick driver for the Atmos
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; Can be used multiple times when statically linked to the application.
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;
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; 2002-12-20, Based on Ullrich von Bassewitz's code.
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; 2017-11-01, Stefan Haubenthal
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;
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.include "joy-kernel.inc"
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.include "joy-error.inc"
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.include "atmos.inc"
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.macpack module
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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module_header _atmos_ijk_joy
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; Driver signature
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.byte $6A, $6F, $79 ; "joy"
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.byte JOY_API_VERSION ; Driver API version number
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; Library reference
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.addr $0000
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; Jump table.
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.addr INSTALL
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.addr UNINSTALL
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.addr COUNT
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.addr READ
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; ------------------------------------------------------------------------
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; Constants
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JOY_COUNT = 2 ; Number of joysticks we support
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present and determine the amount of
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; memory available.
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; Must return an JOY_ERR_xx code in a/x.
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;
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INSTALL:
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lda #%11000000
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sta VIA::DDRA
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sta VIA::PRA
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lda VIA::PRA
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and #%00100000
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bne ijkPresent
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lda #JOY_ERR_NO_DEVICE
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.byte $2C ; Skip next opcode
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ijkPresent:
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lda #JOY_ERR_OK
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.assert JOY_ERR_OK = 0, error
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tax
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; rts ; Run into UNINSTALL instead
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; ------------------------------------------------------------------------
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; UNINSTALL routine. Is called before the driver is removed from memory.
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; Can do cleanup or whatever. Must not return anything.
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;
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UNINSTALL:
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rts
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; ------------------------------------------------------------------------
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; COUNT: Return the total number of available joysticks in a/x.
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;
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COUNT:
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lda #<JOY_COUNT
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ldx #>JOY_COUNT
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rts
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; ------------------------------------------------------------------------
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; READ: Read a particular joystick passed in A.
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;
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READ:
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bne right
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; Ensure Printer Strobe is set to Output
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lda #%10110111
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sta VIA::DDRB
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; Set Strobe Low
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lda #%00000000
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sta VIA::PRB
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; Set Top two bits of PortA to Output and rest as Input
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lda #%11000000
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sta VIA::DDRA
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; Select Left Joystick
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lda #%01111111
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sta VIA::PRA
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; Read back Left Joystick state
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lda VIA::PRA
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; Mask out unused bits
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and #%00011111
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; Invert Bits
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eor #%00011111
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; Index table to conform to Generic Format
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tax
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lda GenericIJKBits,X
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bne L1
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right:
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; Select Right Joystick
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lda #%10111111
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sta VIA::PRA
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; Read back Right Joystick state and rejig bits
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lda VIA::PRA
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and #%00011111
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eor #%00011111
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tax
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lda GenericIJKBits,X
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; Restore VIA PortA state
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L1: ldx #%11111111
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stx VIA::DDRA
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inx ; x=0
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rts
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.rodata
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GenericIJKBits:
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.byte 0,2,1,3,32,34,33,0,8,10,9,0,40,42,41,0
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.byte 16,18,17,0,48,50,49,0,0,0,0,0,0,0,0,0
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