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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_ */