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CS8900A-IQ 参数 Datasheet PDF下载

CS8900A-IQ图片预览
型号: CS8900A-IQ
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  
3.9.5.6 Late Collisions  
gorithms: the Standard Backoff algorithm  
(ISO/IEC 4.2.3.2.5) or the Modified Backoff algo-  
rithm. The host selects which algorithm through  
the ModBackoffE bit (Register 13, LineCTL,  
Bit B).  
If a collision is detected after the first 512 bits have  
been transmitted, the MAC immediately terminates  
transmission, transmits the jam sequence, discards  
the packet, and sets the Out-of-window bit (Regis-  
ter 8, TxEvent, Bit 9). The CS8900A does not ini-  
tiate backoff or attempt to retransmit the frame. For  
additional information about Late Collisions, see  
Out-of-Window Error in this section.  
3.9.5.8 Standard Backoff  
The Standard Backoff algorithm, also called the  
"Truncated Binary Exponential Backoff", is de-  
scribed by the equation:  
3.9.5.7 Backoff  
0 r 2k  
After the MAC has completed transmitting the jam  
sequence, it must wait, or "Back off", before at-  
tempting to transmit again. The amount of time it  
must wait is determined by one of two Backoff al-  
where r (a random integer) is the number of slot  
times the MAC must wait (1 slot time = 512 bit  
times), and k is the smaller of n or 10, where n is the  
number of retransmission attempts.  
3.9.5.9 Modified Backoff  
Start Monitoring  
Network Activity  
The Modified Backoff is described by the equation:  
0 r 2k  
where r (a random integer) is the number of slot  
times the MAC must wait, and k is 3 for n < 3 and  
k is the smaller of n or 10 for n 3, where n is the  
number of retransmission attempts.  
Yes  
Network  
Active?  
No  
The advantage of the Modified Backoff algorithm  
over the Standard Backoff algorithm is that it re-  
duces the possibility of multiple collisions on the  
first three retries. The disadvantage is that it ex-  
tends the maximum time needed to gain access to  
the network for the first three retries.  
Wait  
9.6 µs  
The host may choose to disable the Backoff algo-  
rithm altogether by setting the DisableBackoff bit  
(Register 19, TestCTL, Bit B). When disabled, the  
CS8900A only waits the 9.6 µs IPG time before  
starting transmission.  
No  
T
x
Fra e  
m
Ready and Not  
ac off?  
No  
Yes  
Network  
Active?  
i
n
B
k
3.9.5.10 SQE Test  
Yes  
If the CS8900A is transmitting on the AUI, the ex-  
ternal transceiver should generate an SQE Test sig-  
nal on the CI+/CI- pair following each  
transmission. The SQE Test is a 10 MHz signal  
lasting 5 to 15 bit times and starting within 0.6 to  
Transmit  
Frame  
Figure 11. Simple Deferral  
CIRRUS LOGIC PRODUCT DATA SHEET  
DS271PP3  
33  
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