PROGRAMMING ENVIRONMENT
3-16
The most efficient way to move data blocks longer than 16 bytes is to move them in quad-word
increments, using quad-word instructions
ldq
and
stq
.
Normally when a data block is stored in memory, the block’s least significant byte is stored at a
base memory address and the more significant bytes are stored at successively higher byte
addresses. This method of ordering bytes in memory is referred to as “little endian” ordering.
The i960 Jx processor also provides an option for ordering bytes in the opposite manner in
memory. The block’s most significant byte is stored at the base address and the less significant
bytes are stored at successively higher addresses. This byte-ordering scheme, referred to as “big
endian”, applies to data blocks which are short-words or words. For more about byte ordering, see
section 13.6.2, “Selecting the Byte Order” (pg. 13-12)
.
When loading a byte, short-word or word from memory to a register, the block’s least significant
bit is always loaded in register bit 0. When loading double-words, triple-words and quad-words,
the least significant word is stored in the base register. The more significant words are then stored
at successively higher-numbered registers. Individual bits can be addressed only in data that
resides in a register: bit 0 in a register is the least significant bit, bit 31 is the most significant bit.
3.5.4
Internal Data RAM
Internal data RAM is mapped to the lower 1 Kbyte (0000H to 03FFH) of the address space. Loads
and stores, with target addresses in internal data RAM, operate directly on the internal data RAM;
no external bus activity is generated. Data RAM allows time-critical data storage and retrieval
without dependence on external bus performance. The lower 1 Kbyte of memory is data memory
only. Instructions cannot be fetched from the internal data RAM. Instruction fetches directed to the
data RAM cause a OPERATION.UNIMPLEMENTED fault to occur. For more specific
information refer to
Section 4.1, ”INTERNAL DATA RAM” (pg. 4-1)
3.5.5
Instruction Cache
The instruction cache enhances performance by reducing the number of instruction fetches from
external memory. The cache provides fast execution of cached code and loop functions in addition
to providing more bus bandwidth for data operations in external memory. The i960 JT processor
instruction cache is a 16 Kbyte two-way set-associative. The i960 JF and JD processor instruction
cache is a 4 Kbyte, two-way set-associative, organized in two sets of four-word lines. The i960 JA
processors feature a 2 Kbyte instruction cache two-way set-associative.
Содержание i960 Jx
Страница 1: ...Release Date December 1997 Order Number 272483 002 i960 Jx Microprocessor Developer s Manual ...
Страница 24: ......
Страница 25: ...1 INTRODUCTION ...
Страница 26: ......
Страница 35: ...2 DATA TYPES AND MEMORY ADDRESSING MODES ...
Страница 36: ......
Страница 46: ......
Страница 47: ...3 PROGRAMMING ENVIRONMENT ...
Страница 48: ......
Страница 73: ...4 CACHE AND ON CHIP DATA RAM ...
Страница 74: ......
Страница 85: ...5 INSTRUCTION SET OVERVIEW ...
Страница 86: ......
Страница 111: ...6 INSTRUCTION SET REFERENCE ...
Страница 112: ......
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 ...
Страница 234: ......
Страница 256: ......
Страница 257: ...8 FAULTS ...
Страница 258: ......
Страница 291: ...9 TRACING AND DEBUGGING ...
Страница 292: ......
Страница 309: ...10 TIMERS ...
Страница 310: ......
Страница 324: ......
Страница 325: ...11 INTERRUPTS ...
Страница 326: ......
Страница 369: ...12 INITIALIZATION AND SYSTEM REQUIREMENTS ...
Страница 370: ......
Страница 412: ......
Страница 413: ...13 MEMORY CONFIGURATION ...
Страница 414: ......
Страница 429: ...14 EXTERNAL BUS ...
Страница 430: ......
Страница 468: ......
Страница 469: ...15 TEST FEATURES ...
Страница 470: ......
Страница 493: ...A CONSIDERATIONS FOR WRITING PORTABLE CODE ...
Страница 494: ......
Страница 502: ......
Страница 503: ...B OPCODES AND EXECUTION TIMES ...
Страница 504: ......
Страница 515: ...C MACHINE LEVEL INSTRUCTION FORMATS ...
Страница 516: ......
Страница 523: ...D REGISTER AND DATA STRUCTURES ...
Страница 524: ......
Страница 550: ......
Страница 551: ...GLOSSARY ...
Страница 552: ......
Страница 561: ...INDEX ...
Страница 562: ......
Страница 578: ......