m68302.h

Go to the documentation of this file.

/*
 * COPYRIGHT 1995 David W. Glessner.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the following conditions are met:
 * 1. Redistribution of source code and documentation must retain
 *    the above copyright notice, this list of conditions and the
 *    following disclaimer.
 * 2. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * This software is provided "AS IS" without warranty of any kind,
 * either expressed or implied, including, but not limited to, the
 * implied warranties of merchantability, title and fitness for a
 * particular purpose.
 *
 *------------------------------------------------------------------
 */

#ifndef _RTEMS_M68K_M68302_H
#define _RTEMS_M68K_M68302_H

/*
 * BAR - Base Address Register
 * Section 2.7
 */
#define M302_BAR    (*((volatile uint16_t   *) 0xf2))

/*
 * SCR - System Control Register
 * Section 3.8.1
 */
#define M302_SCR    (*((volatile uint32_t   *) 0xf4))
/*
 * SCR bits
 */
#define RBIT_SCR_IPA        0x08000000
#define RBIT_SCR_HWT        0x04000000
#define RBIT_SCR_WPV        0x02000000
#define RBIT_SCR_ADC        0x01000000

#define RBIT_SCR_ERRE       0x00400000
#define RBIT_SCR_VGE        0x00200000
#define RBIT_SCR_WPVE       0x00100000
#define RBIT_SCR_RMCST      0x00080000
#define RBIT_SCR_EMWS       0x00040000
#define RBIT_SCR_ADCE       0x00020000
#define RBIT_SCR_BCLM       0x00010000

#define RBIT_SCR_FRZW       0x00008000
#define RBIT_SCR_FRZ2       0x00004000
#define RBIT_SCR_FRZ1       0x00002000
#define RBIT_SCR_SAM        0x00001000
#define RBIT_SCR_HWDEN      0x00000800
#define RBIT_SCR_HWDCN2     0x00000400
#define RBIT_SCR_HWDCN1     0x00000200  /* 512 clocks */
#define RBIT_SCR_HWDCN0     0x00000100  /* 128 clocks */

#define RBIT_SCR_LPREC      0x00000080
#define RBIT_SCR_LPP16      0x00000040
#define RBIT_SCR_LPEN       0x00000020
#define RBIT_SCR_LPCLKDIV   0x0000001f


/*
 * 68000 interrupt and trap vector numbers
 */
#define M68K_IVEC_BUS_ERROR      2
#define M68K_IVEC_ADDRESS_ERROR      3
#define M68K_IVEC_ILLEGAL_OPCODE     4
#define M68K_IVEC_ZERO_DIVIDE        5
#define M68K_IVEC_CHK            6
#define M68K_IVEC_TRAPV          7
#define M68K_IVEC_PRIVILEGE      8
#define M68K_IVEC_TRACE          9
#define M68K_IVEC_LINE_A        10
#define M68K_IVEC_LINE_F        11
/*  Unassigned, Reserved        12-14 */
#define M68K_IVEC_UNINITIALIZED_INT 15
/*  Unassigned, Reserved        16-23 */
#define M68K_IVEC_SPURIOUS_INT      24

#define M68K_IVEC_LEVEL1_AUTOVECTOR 25
#define M68K_IVEC_LEVEL2_AUTOVECTOR 26
#define M68K_IVEC_LEVEL3_AUTOVECTOR 27
#define M68K_IVEC_LEVEL4_AUTOVECTOR 28
#define M68K_IVEC_LEVEL5_AUTOVECTOR 29
#define M68K_IVEC_LEVEL6_AUTOVECTOR 30
#define M68K_IVEC_LEVEL7_AUTOVECTOR 31

#define M68K_IVEC_TRAP0         32
#define M68K_IVEC_TRAP1         33
#define M68K_IVEC_TRAP2         34
#define M68K_IVEC_TRAP3         35
#define M68K_IVEC_TRAP4         36
#define M68K_IVEC_TRAP5         37
#define M68K_IVEC_TRAP6         38
#define M68K_IVEC_TRAP7         39
#define M68K_IVEC_TRAP8         40
#define M68K_IVEC_TRAP9         41
#define M68K_IVEC_TRAP10        42
#define M68K_IVEC_TRAP11        43
#define M68K_IVEC_TRAP12        44
#define M68K_IVEC_TRAP13        45
#define M68K_IVEC_TRAP14        46
#define M68K_IVEC_TRAP15        47
/*
 *  Unassigned, Reserved        48-59
 *
 * Note: Vectors 60-63 are used by the MC68302 (e.g. BAR, SCR).
 */

/*
 * MC68302 Interrupt Vectors
 * Section 3.2
 */
enum m68302_ivec_e {
    M302_IVEC_ERR   =0,
    M302_IVEC_PB8   =1, /* General-Purpose Interrupt 0 */
    M302_IVEC_SMC2  =2,
    M302_IVEC_SMC1  =3,
    M302_IVEC_TIMER3    =4,
    M302_IVEC_SCP   =5,
    M302_IVEC_TIMER2    =6,
    M302_IVEC_PB9   =7, /* General-Purpose Interrupt 1 */
    M302_IVEC_SCC3  =8,
    M302_IVEC_TIMER1    =9,
    M302_IVEC_SCC2  =10,
    M302_IVEC_IDMA  =11,
    M302_IVEC_SDMA  =12,    /* SDMA Channels Bus Error */
    M302_IVEC_SCC1  =13,
    M302_IVEC_PB10  =14,    /* General-Purpose Interrupt 2 */
    M302_IVEC_PB11  =15,    /* General-Purpose Interrupt 3 */
    M302_IVEC_IRQ1  =17,    /* External Device */
    M302_IVEC_IRQ6  =22,    /* External Device */
    M302_IVEC_IRQ7  =23 /* External Device */
};


/*
 * GIMR - Global Interrupt Mode Register
 * Section 3.2.5.1
 */
#define RBIT_GIMR_MOD       (1<<15)
#define RBIT_GIMR_IV7       (1<<14)
#define RBIT_GIMR_IV6       (1<<13)
#define RBIT_GIMR_IV1       (1<<12)
#define RBIT_GIMR_ET7       (1<<10)
#define RBIT_GIMR_ET6       (1<<9)
#define RBIT_GIMR_ET1       (1<<8)
#define RBIT_GIMR_VECTOR    (7<<5)

/*
 * IPR - Interrupt Pending Register    (Section 3.2.5.2)
 * IMR - Interrupt Mask Register       (Section 3.2.5.3)
 * ISR - Interrupt In-Service Register (Section 3.2.5.4)
 */
#define RBIT_IPR_PB11       (1<<15)
#define RBIT_IPR_PB10       (1<<14)
#define RBIT_IPR_SCC1       (1<<13)
#define RBIT_IPR_SDMA       (1<<12)
#define RBIT_IPR_IDMA       (1<<11)
#define RBIT_IPR_SCC2       (1<<10)
#define RBIT_IPR_TIMER1     (1<<9)
#define RBIT_IPR_SCC3       (1<<8)
#define RBIT_IPR_PB9        (1<<7)
#define RBIT_IPR_TIMER2     (1<<6)
#define RBIT_IPR_SCP        (1<<5)
#define RBIT_IPR_TIMER3     (1<<4)
#define RBIT_IPR_SMC1       (1<<3)
#define RBIT_IPR_SMC2       (1<<2)
#define RBIT_IPR_PB8        (1<<1)
#define RBIT_IPR_ERR        (1<<0)

#define RBIT_ISR_PB11       (1<<15)
#define RBIT_ISR_PB10       (1<<14)
#define RBIT_ISR_SCC1       (1<<13)
#define RBIT_ISR_SDMA       (1<<12)
#define RBIT_ISR_IDMA       (1<<11)
#define RBIT_ISR_SCC2       (1<<10)
#define RBIT_ISR_TIMER1     (1<<9)
#define RBIT_ISR_SCC3       (1<<8)
#define RBIT_ISR_PB9        (1<<7)
#define RBIT_ISR_TIMER2     (1<<6)
#define RBIT_ISR_SCP        (1<<5)
#define RBIT_ISR_TIMER3     (1<<4)
#define RBIT_ISR_SMC1       (1<<3)
#define RBIT_ISR_SMC2       (1<<2)
#define RBIT_ISR_PB8        (1<<1)

#define RBIT_IMR_PB11       (1<<15)     /* PB11   Interrupt Mask */
#define RBIT_IMR_PB10       (1<<14)     /* PB10   Interrupt Mask */
#define RBIT_IMR_SCC1       (1<<13)     /* SCC1   Interrupt Mask */
#define RBIT_IMR_SDMA       (1<<12)     /* SDMA   Interrupt Mask */
#define RBIT_IMR_IDMA       (1<<11)     /* IDMA   Interrupt Mask */
#define RBIT_IMR_SCC2       (1<<10)     /* SCC2   Interrupt Mask */
#define RBIT_IMR_TIMER1     (1<<9)      /* TIMER1 Interrupt Mask */
#define RBIT_IMR_SCC3       (1<<8)      /* SCC3   Interrupt Mask */
#define RBIT_IMR_PB9        (1<<7)      /* PB9    Interrupt Mask */
#define RBIT_IMR_TIMER2     (1<<6)      /* TIMER2 Interrupt Mask */
#define RBIT_IMR_SCP        (1<<5)      /* SCP    Interrupt Mask */
#define RBIT_IMR_TIMER3     (1<<4)      /* TIMER3 Interrupt Mask */
#define RBIT_IMR_SMC1       (1<<3)      /* SMC1   Interrupt Mask */
#define RBIT_IMR_SMC2       (1<<2)      /* SMC2   Interrupt Mask */
#define RBIT_IMR_PB8        (1<<1)      /* PB8    Interrupt Mask */


/*
 * DRAM Refresh
 * Section 3.9
 *
 * The DRAM refresh memory map replaces the SCC2 Tx BD 6 and Tx BD 7
 * structures in the parameter RAM.
 *
 * Access to the DRAM registers can be accomplished by
 * the following approach:
 *
 *  volatile m302_DRAM_refresh_t *dram;
 *  dram = (volatile m302_DRAM_refresh_t *) &m302.scc2.bd.tx[6];
 *
 * Then simply use pointer references (e.g. dram->count = 3).
 */
typedef struct {
    uint16_t    dram_high;  /* DRAM high address and FC */
    uint16_t    dram_low;   /* DRAM low address */
    uint16_t    increment;  /* increment step (bytes/row) */
    uint16_t    count;      /* RAM refresh cycle count (#rows) */
    uint16_t    t_ptr_h;    /* temporary refresh high addr & FC */
    uint16_t    t_ptr_l;    /* temporary refresh low address */
    uint16_t    t_count;    /* temporary refresh cycles count */
    uint16_t    res;        /* reserved */
} m302_DRAM_refresh_t;


/*
 * TMR - Timer Mode Register (for timers 1 and 2)
 * Section 3.5.2.1
 */
#define RBIT_TMR_ICLK_STOP  (0<<1)
#define RBIT_TMR_ICLK_MASTER    (1<<1)
#define RBIT_TMR_ICLK_MASTER16  (2<<1)
#define RBIT_TMR_ICLK_TIN   (3<<1)

#define RBIT_TMR_OM     (1<<5)
#define RBIT_TMR_ORI        (1<<4)
#define RBIT_TMR_FRR        (1<<3)
#define RBIT_TMR_RST        (1<<0)


/*
 * TER - Timer Event Register (for timers 1 and 2)
 * Section 3.5.2.5
 */
#define RBIT_TER_REF    (1<<1)      /* Output Reference Event */
#define RBIT_TER_CAP    (1<<0)      /* Capture Event */


/*
 * SCC Buffer Descriptors and Buffer Descriptors Table
 * Section 4.5.5
 */
typedef struct m302_SCC_bd {
    uint16_t   status;          /* status and control */
    uint16_t   length;          /* data length */
    volatile uint8_t    *buffer;        /* data buffer pointer */
} m302_SCC_bd_t;

typedef struct {
    m302_SCC_bd_t   rx[8];      /* receive buffer descriptors */
    m302_SCC_bd_t   tx[8];      /* transmit buffer descriptors */
} m302_SCC_bd_table_t;


/*
 * SCC Parameter RAM (offset 0x080 from an SCC Base)
 * Section 4.5.6
 *
 * Each SCC parameter RAM area begins at offset 0x80 from each SCC base
 * area (0x400, 0x500, or 0x600 from the dual-port RAM base).
 *
 * Offsets 0x9c-0xbf from each SCC base area compose the protocol-specific
 * portion of the SCC parameter RAM.
 */
typedef struct {
    uint8_t     rfcr;       /* Rx Function Code */
    uint8_t     tfcr;       /* Tx Function Code */
    uint16_t    mrblr;      /* Maximum Rx Buffer Length */
    uint16_t    _rstate;    /* Rx Internal State */
    uint8_t     res2;
    uint8_t     rbd;        /* Rx Internal Buffer Number */
    uint32_t    _rdptr;     /* Rx Internal Data Pointer */
    uint16_t    _rcount;    /* Rx Internal Byte Count */
    uint16_t    _rtmp;      /* Rx Temp */
    uint16_t    _tstate;    /* Tx Internal State */
    uint8_t     res7;
    uint8_t     tbd;        /* Tx Internal Buffer Number */
    uint32_t    _tdptr;     /* Tx Internal Data Pointer */
    uint16_t    _tcount;    /* Tx Internal Byte Count */
    uint16_t    _ttmp;      /* Tx Temp */
} m302_SCC_parameters_t;

/*
 * UART-Specific SCC Parameter RAM
 * Section 4.5.11.3
 */
typedef struct {
    uint16_t    max_idl;    /* Maximum IDLE Characters (rx) */
    uint16_t    idlc;       /* Temporary rx IDLE counter */
    uint16_t    brkcr;      /* Break Count Register (tx) */
    uint16_t    parec;      /* Receive Parity Error Counter */
    uint16_t    frmec;      /* Receive Framing Error Counter */
    uint16_t    nosec;      /* Receive Noise Counter */
    uint16_t    brkec;      /* Receive Break Condition Counter */
    uint16_t    uaddr1;     /* UART ADDRESS Character 1 */
    uint16_t    uaddr2;     /* UART ADDRESS Character 2 */
    uint16_t    rccr;       /* Receive Control Character Register */
    uint16_t    character[8];   /* Control Characters 1 through 8*/
} m302_SCC_UartSpecific_t;
/*
 *  This definition allows for the checking of receive buffers
 *  for errors.
 */

#define RCV_ERR    0x003F

/*
 * UART receive buffer descriptor bit definitions.
 * Section 4.5.11.14
 */
#define RBIT_UART_CTRL   (1<<11)    /* buffer contains a control char */
#define RBIT_UART_ADDR   (1<<10)    /* first byte contains an address */
#define RBIT_UART_MATCH  (1<<9)     /* indicates which addr char matched */
#define RBIT_UART_IDLE   (1<<8)     /* buffer closed due to IDLE sequence */
#define RBIT_UART_BR     (1<<5)     /* break sequence was received */
#define RBIT_UART_FR     (1<<4)     /* framing error was received */
#define RBIT_UART_PR     (1<<3)     /* parity error was received */
#define RBIT_UART_OV     (1<<1)     /* receiver overrun occurred */
#define RBIT_UART_CD     (1<<0)     /* carrier detect lost */
#define RBIT_UART_STATUS 0x003B     /* all status bits */

/*
 * UART transmit buffer descriptor bit definitions.
 * Section 4.5.11.15
 */
#define RBIT_UART_CR       (1<<11)  /* clear-to-send report
                     * this results in two idle bits
                     * between back-to-back frames
                     */
#define RBIT_UART_A        (1<<10)  /* buffer contains address characters
                     * only valid in multidrop mode (UM0=1)
                     */
#define RBIT_UART_PREAMBLE (1<<9)   /* send preamble before data */
#define RBIT_UART_CTS_LOST (1<<0)   /* CTS lost */

/*
 * UART event register
 * Section 4.5.11.16
 */
#define M302_UART_EV_CTS   (1<<7)   /* CTS status changed */
#define M302_UART_EV_CD    (1<<6)   /* carrier detect status changed */
#define M302_UART_EV_IDL   (1<<5)   /* IDLE sequence status changed */
#define M302_UART_EV_BRK   (1<<4)   /* break character was received */
#define M302_UART_EV_CCR   (1<<3)   /* control character received */
#define M302_UART_EV_TX    (1<<1)   /* buffer has been transmitted */
#define M302_UART_EV_RX    (1<<0)   /* buffer has been received */


/*
 * HDLC-Specific SCC Parameter RAM
 * Section 4.5.12.3
 *
 * c_mask_l should be 0xF0B8 for 16-bit CRC, 0xdebb for 32-bit CRC
 * c_mask_h is a don't care  for 16-bit CRC, 0x20E2 for 32-bit CRC
 */
typedef struct {
    uint16_t    rcrc_l;     /* Temp Receive CRC Low */
    uint16_t    rcrc_h;     /* Temp Receive CRC High */
    uint16_t    c_mask_l;   /* CRC Mask Low */
    uint16_t    c_mask_h;   /* CRC Mask High */
    uint16_t    tcrc_l;     /* Temp Transmit CRC Low */
    uint16_t    tcrc_h;     /* Temp Transmit CRC High */

    uint16_t    disfc;      /* Discard Frame Counter */
    uint16_t    crcec;      /* CRC Error Counter */
    uint16_t    abtsc;      /* Abort Sequence Counter */
    uint16_t    nmarc;      /* Nonmatching Address Received Cntr */
    uint16_t    retrc;      /* Frame Retransmission Counter */

    uint16_t    mflr;       /* Maximum Frame Length Register */
    uint16_t    max_cnt;    /* Maximum_Length Counter */

    uint16_t    hmask;      /* User Defined Frame Address Mask */
    uint16_t    haddr1;     /* User Defined Frame Address */
    uint16_t    haddr2;     /* " */
    uint16_t    haddr3;     /* " */
    uint16_t    haddr4;     /* " */
} m302_SCC_HdlcSpecific_t;
/*
 * HDLC receiver buffer descriptor bit definitions
 * Section 4.5.12.10
 */
#define RBIT_HDLC_EMPTY_BIT  0x8000 /* buffer associated with BD is empty */
#define RBIT_HDLC_LAST_BIT   0x0800 /* buffer is last in a frame */
#define RBIT_HDLC_FIRST_BIT  0x0400 /* buffer is first in a frame */
#define RBIT_HDLC_FRAME_LEN  0x0020 /* receiver frame length violation */
#define RBIT_HDLC_NONOCT_Rx  0x0010 /* received non-octet aligned frame */
#define RBIT_HDLC_ABORT_SEQ  0x0008 /* received abort sequence */
#define RBIT_HDLC_CRC_ERROR  0x0004 /* frame contains a CRC error */
#define RBIT_HDLC_OVERRUN    0x0002 /* receiver overrun occurred */
#define RBIT_HDLC_CD_LOST    0x0001 /* carrier detect lost */

/*
 * HDLC transmit buffer descriptor bit definitions
 * Section 4.5.12.11
 */
#define RBIT_HDLC_READY_BIT  0x8000 /* buffer is ready to transmit */
#define RBIT_HDLC_EXT_BUFFER 0x4000 /* buffer is in external memory */
#define RBIT_HDLC_WRAP_BIT   0x2000 /* last buffer in bd table, so wrap */
#define RBIT_HDLC_WAKE_UP    0x1000 /* interrupt when buffer serviced */
#define RBIT_HDLC_LAST_BIT   0x0800 /* buffer is last in the frame */
#define RBIT_HDLC_TxCRC_BIT  0x0400 /* transmit a CRC sequence */
#define RBIT_HDLC_UNDERRUN   0x0002 /* transmitter underrun */
#define RBIT_HDLC_CTS_LOST   0x0001 /* CTS lost */

/*
 * HDLC event register bit definitions
 * Section 4.5.12.12
 */
#define RBIT_HDLC_CTS   0x80        /* CTS status changed */
#define RBIT_HDLC_CD    0x40        /* carrier detect status changed */
#define RBIT_HDLC_IDL   0x20        /* IDLE sequence status changed */
#define RBIT_HDLC_TXE   0x10        /* transmit error */
#define RBIT_HDLC_RXF   0x08        /* received frame */
#define RBIT_HDLC_BSY  0x04     /* frame rcvd and discarded due to
                     * lack of buffers
                     */
#define RBIT_HDLC_TXB    0x02       /* buffer has been transmitted */
#define RBIT_HDLC_RXB    0x01       /* received buffer */



typedef struct {
    m302_SCC_bd_table_t          bd;    /* +000 Buffer Descriptor Table */
    m302_SCC_parameters_t        parm;  /* +080 Common Parameter RAM */
    union {             /* +09C Protocol-Specific Parm RAM */
    m302_SCC_UartSpecific_t  uart;
    m302_SCC_HdlcSpecific_t  hdlc;
    } prot;
    uint8_t        res[0x040];  /* +0C0 reserved, (not implemented) */
} m302_SCC_t;


/*
 * Common SCC Registers
 */
typedef struct {
    uint16_t    res1;
    uint16_t    scon;   /* SCC Configuration Register        4.5.2 */
    uint16_t    scm;    /* SCC Mode Register                 4.5.3 */
    uint16_t    dsr;    /* SCC Data Synchronization Register 4.5.4 */
    uint8_t     scce;   /* SCC Event Register  4.5.8.1 */
    uint8_t     res2;
    uint8_t     sccm;   /* SCC Mask Register   4.5.8.2 */
    uint8_t     res3;
    uint8_t     sccs;   /* SCC Status Register 4.5.8.3 */
    uint8_t     res4;
    uint16_t    res5;
} m302_SCC_Registers_t;

/*
 * SCON - SCC Configuration Register
 * Section 4.5.2
 */
#define RBIT_SCON_WOMS  (1<<15)     /* Wired-OR Mode Select (NMSI mode only)
                     * When set, the TXD driver is an
                     * open-drain output */
#define RBIT_SCON_EXTC  (1<<14)     /* External Clock Source */
#define RBIT_SCON_TCS   (1<<13)     /* Transmit Clock Source */
#define RBIT_SCON_RCS   (1<<12)     /* Receive Clock Source */

/*
 * SCM - SCC Mode Register bit definitions
 * Section 4.5.3
 * The parameter-specific mode bits occupy bits 15 through 6.
 */
#define RBIT_SCM_ENR    (1<<3)      /* Enable receiver */
#define RBIT_SCM_ENT    (1<<2)      /* Enable transmitter */


/*
 * Internal MC68302 Registers
 * starts at offset 0x800 from dual-port RAM base
 * Section 2.8
 */
typedef struct {
    /* offset +800 */
    uint16_t    res0;
    uint16_t    cmr;        /* IDMA Channel Mode Register */
    uint32_t    sapr;       /* IDMA Source Address Pointer */
    uint32_t    dapr;       /* IDMA Destination Address Pointer */
    uint16_t    bcr;        /* IDMA Byte Count Register */
    uint8_t     csr;        /* IDMA Channel Status Register */
    uint8_t     res1;
    uint8_t     fcr;        /* IDMA Function Code Register */
    uint8_t     res2;

    /* offset +812 */
    uint16_t    gimr;       /* Global Interrupt Mode Register */
    uint16_t    ipr;        /* Interrupt Pending Register */
    uint16_t    imr;        /* Interrupt Mask Register */
    uint16_t    isr;        /* Interrupt In-Service Register */
    uint16_t    res3;
    uint16_t    res4;

    /* offset +81e */
    uint16_t    pacnt;      /* Port A Control Register */
    uint16_t    paddr;      /* Port A Data Direction Register */
    uint16_t    padat;      /* Port A Data Register */
    uint16_t    pbcnt;      /* Port B Control Register */
    uint16_t    pbddr;      /* Port B Data Direction Register */
    uint16_t    pbdat;      /* Port B Data Register */
    uint16_t    res5;

    /* offset +82c */
    uint16_t    res6;
    uint16_t    res7;

    uint16_t    br0;        /* Base Register   (CS0) */
    uint16_t    or0;        /* Option Register (CS0) */
    uint16_t    br1;        /* Base Register   (CS1) */
    uint16_t    or1;        /* Option Register (CS1) */
    uint16_t    br2;        /* Base Register   (CS2) */
    uint16_t    or2;        /* Option Register (CS2) */
    uint16_t    br3;        /* Base Register   (CS3) */
    uint16_t    or3;        /* Option Register (CS3) */

    /* offset +840 */
    uint16_t    tmr1;       /* Timer Unit 1 Mode Register */
    uint16_t    trr1;       /* Timer Unit 1 Reference Register */
    uint16_t    tcr1;       /* Timer Unit 1 Capture Register */
    uint16_t    tcn1;       /* Timer Unit 1 Counter */
    uint8_t     res8;
    uint8_t     ter1;       /* Timer Unit 1 Event Register */
    uint16_t    wrr;        /* Watchdog Reference Register */
    uint16_t    wcn;        /* Watchdog Counter */
    uint16_t    res9;
    uint16_t    tmr2;       /* Timer Unit 2 Mode Register */
    uint16_t    trr2;       /* Timer Unit 2 Reference Register */
    uint16_t    tcr2;       /* Timer Unit 2 Capture Register */
    uint16_t    tcn2;       /* Timer Unit 2 Counter */
    uint8_t     resa;
    uint8_t     ter2;       /* Timer Unit 2 Event Register */
    uint16_t    resb;
    uint16_t    resc;
    uint16_t    resd;

    /* offset +860 */
    uint8_t     cr;     /* Command Register */
    uint8_t     rese[0x1f];

    /* offset +880, +890, +8a0 */
    m302_SCC_Registers_t scc[3];    /* SCC1, SCC2, SCC3 Registers */

    /* offset +8b0 */
    uint16_t    spmode;     /* SCP,SMC Mode and Clock Cntrl Reg */
    uint16_t    simask;     /* Serial Interface Mask Register */
    uint16_t    simode;     /* Serial Interface Mode Register */
} m302_internalReg_t ;


/*
 * MC68302 dual-port RAM structure.
 * (Includes System RAM, Parameter RAM, and Internal Registers).
 * Section 2.8
 */
typedef struct {
    uint8_t     mem[0x240]; /* +000 User Data Memory */
    uint8_t     res1[0x1c0];    /* +240 reserved, (not implemented) */
    m302_SCC_t      scc1;       /* +400 SCC1 */
    m302_SCC_t      scc2;       /* +500 SCC2 */
    m302_SCC_t      scc3;       /* +600 SCC3 */
    uint8_t     res2[0x100];    /* +700 reserved, (not implemented) */
    m302_internalReg_t  reg;        /* +800 68302 Internal Registers */
} m302_dualPortRAM_t;

/* some useful defines the some of the registers above */


/* ----
   MC68302 Chip Select Registers
      p3-46 2nd Edition

 */
#define BR_ENABLED     1
#define BR_DISABLED    0
#define BR_FC_NULL     0
#define BR_READ_ONLY   0
#define BR_READ_WRITE  2
#define OR_DTACK_0     0x0000
#define OR_DTACK_1     0x2000
#define OR_DTACK_2     0x4000
#define OR_DTACK_3     0x6000
#define OR_DTACK_4     0x8000
#define OR_DTACK_5     0xA000
#define OR_DTACK_6     0xC000
#define OR_DTACK_EXT   0xE000
#define OR_SIZE_64K    0x1FE0
#define OR_SIZE_128K   0x1FC0
#define OR_SIZE_256K   0x1F80
#define OR_SIZE_512K   0x1F00
#define OR_SIZE_1M     0x1E00
#define OR_SIZE_2M     0x1C00
#define OR_MASK_RW     0x0000
#define OR_NO_MASK_RW  0x0002
#define OR_MASK_FC     0x0000
#define OR_NO_MASK_FC  0x0001

#define MAKE_BR(base_address, enable, rw, fc) \
    ((base_address >> 11) | fc | rw | enable)

#define MAKE_OR(bsize, DtAck, RW_Mask, FC_Mask) \
    (DtAck | ((~(bsize - 1) & 0x00FFFFFF) >> 11) | FC_Mask | RW_Mask)

#define __REG_CAT(r, n) r ## n
#define WRITE_BR(csel, base_address, enable, rw, fc) \
          __REG_CAT(m302.reg.br, csel) = MAKE_BR(base_address, enable, rw, fc)
#define WRITE_OR(csel, bsize, DtAck, RW_Mask, FC_Mask) \
          __REG_CAT(m302.reg.or, csel) = MAKE_OR(bsize, DtAck, RW_Mask, FC_Mask)

/* ----
   MC68302 Watchdog Timer Enable Bit

 */
#define WATCHDOG_ENABLE    (1)
#define WATCHDOG_TRIGGER() (m302.reg.wrr = 0x10 | WATCHDOG_ENABLE, m302.reg.wcn = 0)
#define WATCHDOG_TOGGLE()  (m302.reg.wcn = WATCHDOG_TIMEOUT_PERIOD)
#define DISABLE_WATCHDOG() (m302.reg.wrr = 0)

/*
 * Declare the variable that's used to reference the variables in
 * the dual-port RAM.
 */
extern volatile m302_dualPortRAM_t m302;

#endif