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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  
ed by more than 2 to 7 ms and no more than 25 to asserting the internal Collision signal (see  
150 ms (see Section 7.4 on page 113 for 10BASE-  
T timing).  
Section 3.9 on page 28 for collision handling).  
3.12 Attachment Unit Interface (AUI)  
The state of the link segment is reported in the  
LinkOK bit (Register 14, LineST, Bit 7). If the  
HC0E bit (Register 15, SelfCTL, Bit D) is clear, it  
is also indicated by the output of the LINKLED  
pin. If the link is "good", the LinkOK bit is set and  
the LINKLED pin is driven low. If the link is "bad"  
the LinkOK bit is clear and the LINKLED pin is  
high. To disable this feature, the host must set the  
DisableLT bit (Register 19, TestCTL, Bit 7). If  
DisableLT is set, the CS8900A will transmit and  
receive packets independent of the link segment.  
The CS8900A Attachment Unit Interface (AUI)  
provides a direct interface to external 10BASE2,  
10BASE5, and 10BASE-FL Ethernet transceivers.  
It is fully compliant with Section 7 of the Ethernet  
standard (ISO/IEC 8802-3), and as such, is capable  
of driving a full 50-meter AUI cable.  
The AUI consists of three pairs of signals: Data Out  
(DO+/DO-), Data In (DI+/DI-), and Collision In  
(CI+/CI-). To select the AUI, the host should set  
the AUI bit (Register 13, LineCTL, Bit 8). The AUI  
can also be selected automatically as described in  
the previous section (Section 3.10.4 on page 35).  
Figure 15 provides a block diagram of the AUI.  
(For a connection diagram, see Section 7.6 on  
page 121).  
3.11.5 Receive Polarity Detection and Correction  
The CS8900A automatically checks the polarity of  
the receive half of the twisted pair cable. If the po-  
larity is correct, the PolarityOK bit (Register 14,  
LineST, bit C) is set. If the polarity is reversed, the  
PolarityOK bit is clear. If the PolarityDis bit (Reg-  
ister 13, LineCTL, Bit C) is clear, the CS8900A au-  
tomatically corrects a reversal. If the PolarityDis  
bit is set, the CS8900A does not correct a reversal.  
The PolarityOK bit and the PolarityDis bit are in-  
dependent.  
AUI  
Collision  
Detect  
CL+  
CL-  
AUICol (to MAC)  
AUIRX  
-
+
DI+  
DI-  
AUISQL  
AUITX  
ENDEC  
-
+
To detect a reversed pair, the receiver examines re-  
ceived link pulses and the End-of-Frame (EOF) se-  
quence of incoming packets. If it detects at least  
one reversed link pulse and at least four frames in a  
row with negative polarity after the EOF, the re-  
ceive pair is considered reversed. Any data re-  
ceived before the correction of the reversal is  
ignored.  
DO+  
DO-  
Figure 15. AUI  
3.12.1 AUI Transmitter  
The AUI transmitter is a differential driver de-  
signed to drive a 78 cable. It accepts data from  
the ENDEC and transmits it directly on the  
DO+/DO- pins. After transmission has started, the  
CS8900A expects to see the packet "looped-back"  
(or echoed) to the receiver, causing the Carrier  
Sense signal to be asserted. This Carrier Sense  
presence indicates that the transmit signal is getting  
through to the transceiver. If the Carrier Sense sig-  
nal remains deasserted throughout the transmis-  
3.11.6 Collision Detection  
If half-duplex operation is selected (Register 19,  
Bit E, FDX), the CS8900A detects a 10BASE-T  
collision whenever the receiver and transmitter are  
active simultaneously. When a collision is present,  
the Collision Detection circuit informs the MAC by  
CIRRUS LOGIC PRODUCT DATA SHEET  
DS271PP3  
37  
 
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