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// license:BSD-3-Clause
// copyright-holders:Morten Shearman Kirkegaard, Samuel Neves, Peter Wilhelmsen
/*************************************************************************

    atarixga.h
 
    Atari XGA encryption FPGA

*************************************************************************/

#ifndef __MACHINE_ATARIXGA__
#define __MACHINE_ATARIXGA__

extern const device_type ATARI_XGA;

class atari_xga_device :  public device_t
{
public:
    // construction/destruction
    atari_xga_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
    
    DECLARE_WRITE32_MEMBER(write);
    DECLARE_READ32_MEMBER(read);
    
protected:
    virtual void device_start() override;
    virtual void device_reset() override;
    
private:
    static const size_t RAM_WORDS = 2048;
    
    enum fpga_mode
    {
        FPGA_RESET,
        FPGA_SETKEY,
        FPGA_DECIPHER
    };
    
    UINT16 powers2(UINT8 k, UINT16 x);
    UINT16 lfsr2(UINT16 x);
    UINT16 lfsr1(UINT16 x);
    UINT16 parity(UINT16 x);
    size_t popcount(UINT16 x);
    UINT16 ctz(UINT16 x);
    UINT16 decipher(UINT8 k, UINT16 c);

    fpga_mode m_mode;
    UINT16 m_address;    // last written address
    UINT16 m_ciphertext; // last written ciphertext
    std::unique_ptr<UINT16[]> m_ram; // CY7C185-45PC, only 16-Kbit used
};


#endif