EXTERNAL BUS
14-13
14
Figure 14-6. 8-Bit Wide Data Bus Bursts
Burst accesses for a 16-bit bus are always aligned to even short-word boundaries. A four
short-word burst access always begins on a four short-word boundary (A2=0, A1=0). Two
short-word burst accesses always begin on an even short-word boundary (A1=0). Single
short-word transfers occur on single short-word boundaries (see
Figure 14-5
).
Burst accesses for an 8-bit bus are always aligned to even byte boundaries. Four-byte burst
accesses always begin on a 4-byte boundary (A1=0, A0=0). Two-byte burst accesses always begin
on an even byte boundary (A0=0) (see
Figure 14-6
).
Figure 14-7
illustrates a series of bus accesses resulting from a triple-word store request to 16-bit
wide memory. The top half of the figure shows the initial location of 12 data bytes contained in
registers g4 through g6. The instruction’s task is to move this data to memory at address 0AH. The
top half of the figure also shows the final destination of the data.
Notice that a new 16-byte boundary begins at address 10H. Since the processor stores 6 of the 12
bytes after this 16-byte boundary, the processor will split the transaction into a number of accesses.
The i960 Jx processor cannot burst across 16-byte boundaries.
8-Bit Burst Bus
4-Byte Burst
2-Byte Burst
2-Byte Burst
A1:0 = (BE1, BE0)
00
10
11
01
Содержание i960 Jx
Страница 1: ...Release Date December 1997 Order Number 272483 002 i960 Jx Microprocessor Developer s Manual ...
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Страница 25: ...1 INTRODUCTION ...
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Страница 35: ...2 DATA TYPES AND MEMORY ADDRESSING MODES ...
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Страница 47: ...3 PROGRAMMING ENVIRONMENT ...
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Страница 73: ...4 CACHE AND ON CHIP DATA RAM ...
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Страница 85: ...5 INSTRUCTION SET OVERVIEW ...
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Страница 111: ...6 INSTRUCTION SET REFERENCE ...
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Страница 195: ...INSTRUCTION SET REFERENCE 6 83 6 Opcode mov 5CCH REG movl 5DCH REG movt 5ECH REG movq 5FCH REG See Also LOAD STORE lda ...
Страница 233: ...7 PROCEDURE CALLS ...
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Страница 257: ...8 FAULTS ...
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Страница 291: ...9 TRACING AND DEBUGGING ...
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Страница 309: ...10 TIMERS ...
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Страница 325: ...11 INTERRUPTS ...
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Страница 369: ...12 INITIALIZATION AND SYSTEM REQUIREMENTS ...
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Страница 413: ...13 MEMORY CONFIGURATION ...
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Страница 429: ...14 EXTERNAL BUS ...
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Страница 469: ...15 TEST FEATURES ...
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Страница 493: ...A CONSIDERATIONS FOR WRITING PORTABLE CODE ...
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Страница 503: ...B OPCODES AND EXECUTION TIMES ...
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Страница 515: ...C MACHINE LEVEL INSTRUCTION FORMATS ...
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Страница 523: ...D REGISTER AND DATA STRUCTURES ...
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Страница 551: ...GLOSSARY ...
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Страница 561: ...INDEX ...
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