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CS8900A-IQ3 参数 Datasheet PDF下载

CS8900A-IQ3图片预览
型号: CS8900A-IQ3
PDF下载: 下载PDF文件 查看货源
内容描述: 水晶局域网? ISA以太网控制器 [Crystal LAN ⑩ ISA Ethernet Controller]
分类和应用: 控制器局域网以太网
文件页数/大小: 128 页 / 1360 K
品牌: CIRRUS [ CIRRUS LOGIC ]
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CS8900A  
Crystal LAN™ ISA Ethernet Controller  
Host Enters Interrupt Routine  
No  
RxDMA  
Process other events  
that caused interrupt  
Frame  
bit set?  
Yes  
Read the DMA frame Count (CDMA  
(PacketPage base + 0028h)  
)
Yes  
CDMA  
Process other events  
that caused interrupt  
= 0 ?  
No  
Process the  
DMA Frames  
C
Figure 25. RxDMA Only Operation  
5.5.2 Configuring the CS8900A for Auto-Switch  
5.5.3 Auto-Switch DMA Operation  
DMA  
Whenever a frame begins to be received in Auto-  
Switch DMA mode, the CS8900A checks to see if  
there is enough on-chip buffer space to store a max-  
imum length frame. If there is, the incoming frame  
is pre-processed and buffered as normal. If there  
isnt, the CS8900As MAC engine compares the  
frames Destination Address (DA) to the criteria  
programmed into the DA filter. If the incoming DA  
fails the DA filter, the frame is discarded. If the DA  
passes the DA filter, the CS8900A automatically  
switches to DMA mode and starts transferring the  
frame(s) currently being held in the on-chip buffer  
into host memory. This frees up buffer space for the  
incoming frame.  
Auto-Switch DMA mode requires the same config-  
uration as Receive-DMA-only mode, with one ex-  
ception: the AutoRxDMAE bit (Register 3,  
RxCFG, Bit A) must be set, and the RxDMAonly  
bit (Register 3, RxCFG, Bit 9) must be clear (see  
Section 5.4 on page 90, Configuring the CS8900A  
for DMA Operation). In Auto-Switch DMA mode,  
the CS8900A operates in non-DMA mode if possi-  
ble, only switching to slave DMA if necessary.  
Note that if the AutoRxDMAE bit and the RxDM-  
Aonly bit (Register 3, RxCFG, bit 9) are both set,  
the CS8900A uses DMA for all receive frames.  
CIRRUS LOGIC PRODUCT DATA SHEET  
94  
DS271PP3  
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