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CS8900A 参数 Datasheet PDF下载

CS8900A图片预览
型号: CS8900A
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  
the final 3.2 µs). The MAC then begins transmis- mit a packet a total of 16 times (the initial attempt  
sion if a transmit packet is ready and if it is not in  
Backoff (Backoff is described later in this section).  
If no transmit packet is pending, the MAC contin-  
ues to monitor the network. If activity is detected  
plus 15 retransmissions) due to normal collisions.  
On the 16th collision, it sets the 16coll bit  
(Register 8, TxEvent, Bit F) and discards the pack-  
et. If the Onecoll bit is set, the MAC discards the  
before a transmit frame is ready, the MAC defers to packet without attempting any retransmission.  
the transmitting station and resumes monitoring the  
network.  
The two-part deferral scheme was developed to  
prevent the possibility of the IPG being shortened  
due to a temporary loss of carrier. Figure 10 dia-  
Start Monitoring  
Network Activity  
grams the two-part deferral process.  
3.9.5.3 Simple Deferral  
In the simple deferral scheme, the IPG timer is  
Yes  
Network  
Active?  
started whenever Carrier Sense is deasserted. Once  
the IPG timer is finished (after 9.6 µs), if a transmit  
frame is pending and if the MAC is not in Backoff,  
No  
transmission begins the 9.6 µs IPG). If no transmit  
packet is pending, the MAC continues to monitor  
Start IPG  
Timer  
the network. If activity is detected before a transmit  
frame is ready, the MAC defers to the transmitting  
station and resumes monitoring the network. Fig-  
ure 11 diagrams the simple deferral process.  
IPG  
Timer =  
Yes  
6.4 s?  
µ
3.9.5.4 Collision Resolution  
No  
Wait  
3.2  
If a collision is detected while the CS8900A is  
transmitting, the MAC responds in one of three  
ways depending on whether it is a normal collision  
(within the first 512 bits of transmission) or a late  
collision (after the first 512 bits of transmission):  
µ
s
No  
Network  
Active?  
Yes  
3.9.5.5 Normal Collisions  
If a collision is detected before the end of the pre-  
amble and SFD, the MAC finishes the preamble  
and SFD, transmits the jam sequence (32-bit pat-  
tern of all 0’s), and then initiates Backoff. If a col-  
lision is detected after the transmission of the  
preamble and SFD but before 512 bit times, the  
MAC immediately terminates transmission, trans-  
mits the jam sequence, and then initiates Backoff.  
In either case, if the Onecoll bit (Register 9, TxC-  
MD, Bit 9) is clear, the MAC will attempt to trans-  
No  
Tx  
Frame  
Ready and Not  
in Backoff?  
No  
Yes  
Network  
Active?  
Yes  
Transmit  
Frame  
Figure 10. Two-Part Deferral  
CIRRUS LOGIC PRODUCT DATA SHEET  
32  
DS271PP3