參數(shù)資料
型號: AM79C974
廠商: Advanced Micro Devices, Inc.
英文描述: PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems
中文描述: PCnetTM -的SCSI結(jié)合以太網(wǎng)和SCSI控制器PCI系統(tǒng)
文件頁數(shù): 31/153頁
文件大?。?/td> 838K
代理商: AM79C974
P R E L I M I N A R Y
AMD
31
Am79C974
Bus Acquisition
The Am79C974 microcode (in the buffer management
section) will determine when a DMA transfer should be
initiated. The first step in any Am79C974 bus master
transfer is to acquire ownership of the bus. This task is
handled by synchronous logic within the BIU. Bus own-
ership is requested with the
REQ
signal and ownership
is granted by the arbiter through the
GNT
signal.
Figure 5 shows the Am79C974 controller bus acquisi-
tion.
GNT
is asserted at clock 3. The Am79C974 control-
ler starts driving AD[31:00] and C/
BE
[3:0] prior to clock
4.
FRAME
is asserted at clock 5 indicating a valid ad-
dress and command on AD[31:00] and C/
BE
[3:0].
ADSTEP (bit 7) in the PCI Command register is set to
ONE to indicated that the Am79C974 controller uses ad-
dress stepping. Address stepping is only used for the
first address phase of a bus master period.
18681A-9
FRAME
CLK
AD
C/
BE
REQ
GNT
1
2
3
4
5
ADDR
CMD
Figure 5. Bus Acquisition
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AM79C974KC 制造商:Advanced Micro Devices 功能描述:
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