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/*

 * mmu.h -- memory and TLB access

 */

#ifndef _MMU_H_

#define _MMU_H_

#define TLB_SHFT        5               /* log2 of number of TLB entries */

#define TLB_SIZE        (1 << TLB_SHFT) /* total number of TLB entries */

#define TLB_MASK        (TLB_SIZE - 1)  /* mask for number of TLB entries */

#define TLB_FIXED       4               /* number of fixed TLB entries */

#define TLB_WRITE       (1 << 1)        /* write bit in EntryLo */

#define TLB_VALID       (1 << 0)        /* valid bit in EntryLo */

#define MMU_ACCS_MASK   0x07            /* bits used in BadAccs */

#define MMU_ACCS_READ   0x00            /* access type = read */

#define MMU_ACCS_WRITE  0x04            /* access type = write */

#define MMU_ACCS_BYTE   0x00            /* access width = byte */

#define MMU_ACCS_HALF   0x01            /* access width = half */

#define MMU_ACCS_WORD   0x02            /* access width = word */

typedef struct {

  Word page;            /* 20 high-order bits of virtual address */

  Word frame;           /* 20 high-order bits of physical address */

  Bool write;           /* must be true to allow writing to the page */

  Bool valid;           /* must be true for the entry to be valid */

} TLB_Entry;

Word mmuReadWord(Word vAddr);

Half mmuReadHalf(Word vAddr);

Byte mmuReadByte(Word vAddr);

void mmuWriteWord(Word vAddr, Word data);

void mmuWriteHalf(Word vAddr, Half data);

void mmuWriteByte(Word vAddr, Byte data);

Word mmuGetIndex(void);

void mmuSetIndex(Word value);

Word mmuGetEntryHi(void);

void mmuSetEntryHi(Word value);

Word mmuGetEntryLo(void);

void mmuSetEntryLo(Word value);

Word mmuGetBadAddr(void);

void mmuSetBadAddr(Word value);

Word mmuGetBadAccs(void);

void mmuSetBadAccs(Word value);

TLB_Entry mmuGetTLB(int index);

void mmuSetTLB(int index, TLB_Entry tlbEntry);

#endif /* _MMU_H_ */