CHIP-SELECT UNIT
6-2
Figure 6-1. Common Chip-Select Generation Methods
6.3
CHIP-SELECT UNIT FUNCTIONAL OVERVIEW
The Chip-Select Unit (CSU) decodes bus cycle address and status information and enables the
appropriate chip-select. Figure 6-3 illustrates the timing of a chip-select during a bus cycle. Note
that the chip-select goes active in the same bus state as address goes active, eliminating any delay
through address latches and decoder circuits. The Chip-Select Unit activates a chip-select for bus
cycles initiated by the CPU, DMA Control Unit or Refresh Control Unit.
Six of the chip-selects map only into memory address space, while the remaining seven can map
into either memory or I/O address space. The chip-selects typically associate with memory and
peripheral devices as follows:
27C256
A1:13
A16
A0:12
D15:8
(A)
RD
CS
Chip-Selects Using
Addresses Directly
(B)
HLDA
74AC138
E3
ALE
A19
A18
A17
A3
A2
A1
E1
E2
Selects 768K to 896K
Selects 896K to 1M
Selects 128K to 256K
Selects 0 to 128K
Chip-Selects Using
Simple Decoder
OE
Y7
Y6
Y5
Y4
Y3
Y2
Y1
Y0
D7:0
A1168-0A
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...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
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...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
Страница 229: ......
Страница 253: ......
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...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
Страница 373: ......
Страница 396: ...Index...
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