EXTERNAL BUS
14-8
During initialization, the bus configuration data is read from the Initialization Boot Record (IBR)
assuming an 8-bit bus width; however, the IBR can be in 8-bit, 16-bit, or 32-bit physical memory.
BE3 and BE2 are defined as “1” so that reading the bus configuration data works for all bus
widths. Since these byte enables are ignored for actual 8-bit memory, they can be permanently
defined this way for ease of implementation.
Table 14-2. 8-Bit Bus Width Byte Enable Encodings
Byte
BE3
(Not Used)
BE2
(Not Used)
BE1
(Used as A1)
BE0
(Used as A0)
0
1
1
0
0
1
1
1
0
1
2
1
1
1
0
3
1
1
1
1
Table 14-3. 16-Bit Bus Width Byte Enable Encodings
Byte
BE3
(Used as BHE)
BE2
(Not Used)
BE1
(Used as A1)
BE0
(Used as BLE)
0,1
0
1
0
0
2,3
0
1
1
0
0
1
1
0
0
1
0
1
0
1
2
1
1
1
0
3
0
1
1
1
Table 14-4. 32-Bit Bus Width Byte Enable Encodings
Byte
BE3
BE2
BE1
BE0
0,1,2,3
0
0
0
0
0,1
1
1
0
0
2,3
0
0
1
1
0
1
1
1
0
1
1
1
0
1
2
1
0
1
1
3
0
1
1
1
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 ...
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Страница 550: ......
Страница 551: ...GLOSSARY ...
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Страница 561: ...INDEX ...
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