6-15
CHIP-SELECT UNIT
6.4.2.4 PCS Active Range
Each PCS chip-select starts at an offset above the base address programmed in the PACS register
and is active for 128 bytes. The base address can start on any 1 Kbyte memory or I/O address
location. Table 6-6 lists the active range for each PCS chip-select.
6.4.3 Bus Wait State and Ready Control
Normally, the bus ready input must be inactive at the appropriate time to insert wait states into
the bus cycle. The Chip-Select Unit can ignore the state of the bus ready input to extend and com-
plete the bus cycle automatically. Most memory and peripheral devices operate properly using
three or fewer wait states. However, accessing such devices as a dual-port memory, an expansion
bus interface, a system bus interface or remote peripheral devices can require more than three
wait states to complete a bus cycle.
A three-bit field (R2:0) in the control registers defines the number of wait states and the ready
requirements for the chip-selects. Figure 6-11 shows a simplified logic diagram of the wait state
and ready control functions.
Table 6-6. PCS Active Range
Chip-
Select
Active Range
Start Address
Ending Address
PCS0
Base
Base + 127 (7FH)
PCS1
Base + 128 (080H)
Base + 255 (0FFH)
PCS2
Base + 256 (100H)
Base + 383 (17FH)
PCS3
Base + 384 (180H)
Base + 511 (1FFH)
PCS4
Base + 512 (200H)
Base + 639 (27FH)
PCS5
Base + 640 (280H)
Base + 767 (2FFH)
PCS6
Base + 768 (300H)
Base + 895 (37FH)
Содержание 80C186EA
Страница 1: ...80C186EA 80C188EA Microprocessor User s Manual...
Страница 2: ...80C186EA 80C188EA Microprocessor User s Manual 1995...
Страница 19: ......
Страница 20: ...1 Introduction...
Страница 21: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
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Страница 130: ...4 Peripheral Control Block...
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Страница 140: ...5 ClockGenerationand Power Management...
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Страница 166: ...6 Chip Select Unit...
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Страница 190: ...7 Refresh Control Unit...
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Страница 206: ...8 Interrupt Control Unit...
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Страница 239: ...INTERRUPT CONTROL UNIT 8 32...
Страница 240: ...9 Timer Counter Unit...
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Страница 266: ...10 Direct Memory Access Unit...
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Страница 295: ...DIRECT MEMORY ACCESS UNIT 10 28...
Страница 296: ...11 Math Coprocessing...
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Страница 314: ...12 ONCE Mode...
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Страница 318: ...A 80C186 Instruction Set Additions and Extensions...
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Страница 330: ...B Input Synchronization...
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Страница 334: ...C Instruction Set Descriptions...
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Страница 383: ...INSTRUCTION SET DESCRIPTIONS C 48...
Страница 384: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 408: ...Index...
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