EXTERNAL BUS
14-9
14
Intel designed the i960 Jx processor to drive determinate values on all address/data pins during
Tw/Td write operation states. For an 8-bit bus, the processor continues to drive address on unused
data pins AD31:8. For a 16-bit bus, the processor continues to drive address on unused data pins
AD31:16. However, when the processor does not use the entire bus width because of data width or
misalignment (i.e., 8-bit write on a 16- or 32-bit bus or a 16-bit write on a 32-bit bus), data is
replicated on those unused portions of the bus.
14.2.3.2
Basic Bus Accesses
The basic transaction is a read or write of one data word. The first half of
Figure 14-3
shows a typical
timing diagram for a non-burst, 32-bit read transaction. For simplicity, no wait states are shown.
During the Ta state, the i960 Jx microprocessor transmits the address on the address/data lines. In
the figure, the size bits (AD1:0) specify a single word transaction and WIDTH1:0 indicate a 32-bit
wide access. The processor asserts ALE to latch the address and drives ADS low to denote the start
of the cycle. BE3:0 specify which bytes the processor uses to read the data word. The processor
brings W/R low to denote a read operation and drives D/C to the proper state. For data trans-
ceivers, DT/R goes low to define the input direction.
During the Tw/Td state, the i960 Jx microprocessor deasserts ADS and asserts DEN to enable any
data transceivers. Since this is a non-burst transaction, the processor asserts BLAST to signify the
last transfer of a transaction. The figure shows RDYRCV assertion by external logic, so this state
is a data state and the processor latches data on a rising CLKIN edge.
The Tr state follows the Tw/Td state. This allows the system components adequate time to remove
their outputs from the bus before the processor drives the next address on the address/data lines.
During the Tr state, BLAST, BE3:0 and DEN are inactive. W/R and DT/R hold their previous values.
The figure indicates a logical high for the RDYRCV pin, so there is only one recovery state.
After a read, notice that the address/data bus goes to an invalid state during Ti. The processor
drives valid logic levels on the address/data bus instead of allowing it to float. See
section 14.2.4,
“Bus and Control Signals During Recovery and Idle States” (pg. 14-22)
for the values that are
driven during Ti.
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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