;;********************************************************************************
;; @module IO-W65C22
;; @type utility
;; @device Western Design - W65C22N Versatile Interface Adapter
;; @details
;;********************************************************************************

.ifndef INCLUDE_IOW65C22
INCLUDE_IOW65C22 = 1

;;********************************************************************************
;; @brief Versatile Interface Adapter (VIA) W65C22
;; @ingroup utility
;; @device Western Design - W65C22N Versatile Interface Adapter
;; @todo rename to VIA
;; @warning @anchor via_hardware_bug
;;  The 6522 and 65C22 have a hardware bug, where a bit is not read in when the 
;;  external shift register clock transitions close to @f$ \phi_2 @f$.
;;  To resolve this, you should use a @f$ \phi_2 @f$ controlled flip flop to ensure
;;  the external clock transitions after the system clock.
;;********************************************************************************
.scope IO

; not using a struct for this since the syntax for access would be the same, 
; ie label+IO::RA
;;********************************************************************************
;; @brief VIA register offsets from the base address 
;; @details
;;  Use like this: `VIA_ADDRESS + IO::RB`
;;********************************************************************************
.enum
    RB   = $0  ;; Register B (ORB/IRB)
    RA   = $1  ;; Register A (ORA/IRA)
    DDRB = $2  ;; Data Direction Register B
    DDRA = $3  ;; Data Direction Register A
    T1CL = $4  ;; Timer 1 Counter Low/High
    T1CH = $5
    T1LL = $6  ;; Timer 1 Latch Low/High
    T1LH = $7
    T2CL = $8  ;; Timer 2 Counter Low/High
    T2CH = $9
    SR   = $a  ;; Shift Register
    ACR  = $b  ;; Auxiliary Control Register
    PCR  = $c  ;; Peripheral Control Register
    IFR  = $d  ;; Interrupt Flag Register
    IER  = $e  ;; Interrupt Enable Register
    RANH = $f  ;; RA without handshake
.endenum

.enum ACR_MASK  ; ACR Masks
    PA          = %00000001
    PB          = %00000010
    SR          = %00011100
    T2          = %00100000
    T1          = %11000000
.endenum

;;********************************************************************************
;; @brief Settings for Auxiliary Control Register
;; @details
;;  `OR` the values with the appropriate IO::ACR_MASK to not target only specific settings
;;********************************************************************************
.enum ACR
    ; SR Modes
    SR_DISABLE       = %00000000  ;; Disabled
    SR_SIN_T2        = %00000100  ;; Shift in under control of T2
    SR_SIN_PHI2      = %00001000  ;; Shift in under control of PHI2
    SR_SIN_PHIE      = %00001100  ;; Shift in under control of external clock
    SR_SOUT_FREE_T2  = %00010000  ;; Shift out free running at T2 rate
    SR_SOUT_T2       = %00010100  ;; Shift out under control of T2
    SR_SOUT_PHI2     = %00011000  ;; Shift out under control of PHI2
    SR_SOUT_PHIE     = %00011100  ;; Shift out under control of external clock
    ; T1 Modes
    T1_IRQ_LOAD      = %00000000  ;; Timed interrupt each time T1 is loaded
    T1_IRQ_CONT      = %01000000  ;; Continuous interrupts
    T1_IRQ_LOAD_PB7  = %10000000  ;; Timed interrupt each time T1 is loaded - PB7 One Shot output
    T1_IRQ_CONT_PB7  = %11000000  ;; Continuous interrupts - PB7 Square wave output
    ; T2 Modes
    T2_IRQ_LOAD      = %00000000  ;; Timed interrupt each time T2 is loaded
    T2_COUNT_PB6     = %00100000  ;; Count down with pulsen on PB6
    ; Latch
    LATCH_DISABLE    = %00000000  ;; `OR` this with IO::ACR_MASK::PA or IO::ACR_MASK::PB
    LATCH_ENBLE      = %00000011  ;; `OR` this with IO::ACR_MASK::PA or IO::ACR_MASK::PB
.endenum

.enum PCR_MASK  ; PCR Masks
    CA1         = %00000001  ; 
    CA2         = %00001110  ; 
    CB1         = %00010000  ; 
    CB2         = %11100000  ; 
.endenum

;;********************************************************************************
;; @brief Settings for Peripheral Control Register
;; @details
;;  `OR` the values with the appropriate IO::PCR_MASK to not target only specific settings
;;********************************************************************************
.enum PCR
    ; CA1 Modes
    CA1_IN_AE        = %00000000   ; Input-negative active edge
    CA1_IP_AE        = %00000001   ; Input-positive active edge
    ; CA2 Modes
    CA2_IN_AE        = %00000000  ; Input-negative active edge
    CA2_IN_AE_IRQ_IND= %00000010  ; Independent interrupt input-negative edge
    CA2_IP_AE        = %00000100  ; Input-positive active edge
    CA2_IP_AE_IRQ_IND= %00000110  ; Independent interrupt input-positive edge
    CA2_OUT_HANDSHAKE= %00001000  ; Handshake output
    CA2_OUT_PULSE    = %00001010  ; Pulse output
    CA2_OUT_LOW      = %00001100  ; Low output
    CA2_OUT_HIGH     = %00001110  ; High output
    ; CB1 Modes
    CB1_IN_AE        = %00000000   ; Input-negative active edge
    CB1_IP_AE        = %00010000   ; Input-positive active edge
    ; CB2 Modes
    CB2_IN_AE        = %00000000  ; Input-negative active edge
    CB2_IN_AE_IRQ_IND= %00100000  ; Independent interrupt input-negative edge
    CB2_IP_AE        = %01000000  ; Input-positive active edge
    CB2_IP_AE_IRQ_IND= %01100000  ; Independent interrupt input-positive edge
    CB2_OUT_HANDSHAKE= %10000000  ; Handshake output
    CB2_OUT_PULSE    = %10100000  ; Pulse output
    CB2_OUT_LOW      = %11000000  ; Low output
    CB2_OUT_HIGH     = %11100000  ; High output
.endenum


;;********************************************************************************
;; @brief Interrupt Flag/Enable Register bits
;;********************************************************************************
.enum IRQ
    CA2  = %00000001
    CA1  = %00000010
    SR   = %00000100
    CB2  = %00001000
    CB1  = %00010000
    T2   = %00100000
    T1   = %01000000
    IRQ  = %10000000
.endenum

;;********************************************************************************
;; @macro Enable an interrupt source
;; @modifies: A
;; @param flag: A flag of the interrupt flag register (IO::IRQ)
;;********************************************************************************
.macro IO_EnableIRQ ioaddr, flag
    lda #(IO::IRQ::IRQ | flag)
    sta ioaddr + IO::IER
.endmacro
;;********************************************************************************
;; @macro Disable an interrupt source
;; @modifies: A
;; @param flag: A flag of the interrupt flag register (IO::IRQ)
;;********************************************************************************
.macro IO_DisableIRQ ioaddr, flag
    lda #flag
    sta ioaddr + IO::IER
.endmacro

.endscope ; IO
.endif  ; guard