REFRESH CONTROL UNIT
7-12
Example 7-1. Initializing the Refresh Control Unit (Continued)
7.8 REFRESH OPERATION AND BUS HOLD
When another bus master controls the bus, the processor keeps HLDA active as long as the
HOLD input remains active. If the Refresh Control Unit generates a refresh request during bus
hold, the processor drives the HLDA signal inactive, indicating to the current bus master that it
wishes to regain bus control (see Figure 7-9). The BIU begins a refresh bus cycle only after the
alternate master removes HOLD. The user must design the system so that the processor can re-
gain bus control. If the alternate master asserts HOLD after the processor starts the refresh cycle,
the CPU will relinquish control by asserting HLDA when the refresh cycle is complete.
mov dx, RFBASE ;set upper 7 address bits
mov ax, _dram_addr
out dx, al
mov dx, RFTIME ;set clock pre_scaler
mov ax, _clock_time
out dx, al
mov dx, RFCON ;Enable RCU
mov ax, Enable
out dx, al
mov cx, 8 ;8 dummy cycles are
;required by DRAMs
xor di, di ;before actual use
_exercise_ram:
mov word ptr [di], 0
loop _exercise_ram
pop di ;restore saved registers
pop dx
pop cx
pop ax
pop bp ;restore caller’s bp
ret
_config_rcu
endp
lib_80186
ends
end
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...
Страница 81: ......
Страница 129: ......
Страница 130: ...4 Peripheral Control Block...
Страница 131: ......
Страница 139: ......
Страница 140: ...5 ClockGenerationand Power Management...
Страница 141: ......
Страница 165: ......
Страница 166: ...6 Chip Select Unit...
Страница 167: ......
Страница 190: ...7 Refresh Control Unit...
Страница 191: ......
Страница 205: ......
Страница 206: ...8 Interrupt Control Unit...
Страница 207: ......
Страница 239: ...INTERRUPT CONTROL UNIT 8 32...
Страница 240: ...9 Timer Counter Unit...
Страница 241: ......
Страница 265: ......
Страница 266: ...10 Direct Memory Access Unit...
Страница 267: ......
Страница 295: ...DIRECT MEMORY ACCESS UNIT 10 28...
Страница 296: ...11 Math Coprocessing...
Страница 297: ......
Страница 314: ...12 ONCE Mode...
Страница 315: ......
Страница 318: ...A 80C186 Instruction Set Additions and Extensions...
Страница 319: ......
Страница 330: ...B Input Synchronization...
Страница 331: ......
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...
Страница 385: ......
Страница 408: ...Index...
Страница 409: ......