BUS INTERFACE UNIT
3-4
Figure 3-3. 16-Bit Data Bus Even Word Transfers
During a byte read operation, the BIU floats the entire 16-bit data bus, even though the transfer
occurs on only one half of the bus. This action simplifies the decoding requirements for read-only
devices (e.g., ROM, EPROM, Flash). During the byte read, an external device can drive both
halves of the bus, and the BIU automatically accesses the correct half. During the byte write op-
eration, the BIU drives both halves of the bus. Information on the half of the bus not involved in
the transfer is indeterminate. This action requires that the appropriate bank (defined by BHE or
A0 high) be disabled to prevent destroying data.
A19:1
D15:8
D7:0
A0
(Low)
BHE
(Low)
(X)
(X + 1)
A1107-0A
Содержание 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
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Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
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Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
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Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
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Страница 254: ...10 Direct Memory Access Unit...
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Страница 284: ...11 Math Coprocessing...
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Страница 302: ...12 ONCE Mode...
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Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
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Страница 318: ...B Input Synchronization...
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Страница 322: ...C Instruction Set Descriptions...
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Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 396: ...Index...
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