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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  
iE bit (Register 7, TxCFG, Bit 9) is set, the host is  
interrupted. A late collision may indicate an illegal  
network configuration.  
ment of both transmit and receive packets. When  
the TxPadDis bit (Register 9, TxCMD, Bit D) is  
clear, transmit frames will be padded with addition-  
al bits to ensure that the receiving station receives a  
legal frame (64 bytes, including CRC). When Tx-  
PadDis is set, the CS8900A will not add pad bits  
and will transmit frames less that 64 bytes. If a  
frame is received that is less than 64 bytes (includ-  
ing CRC), the Runt bit (Register 4, RxEvent, Bit D)  
will be set indicating the arrival of an illegal frame.  
3.9.3.4 Jabber Error  
If a transmission continues longer than about  
26 ms, the MAC disables the transmitter and sets  
the Jabber bit (Register 8, TxEvent, Bit A). The  
output of the transmitter returns to idle and remains  
there until the host issues a new Transmit Com-  
mand. If the JabberiE bit (Register 7, TxCFG, Bit  
A) is set, the host is interrupted. A Jabber condition  
indicates that there may be something wrong with  
the CS8900A transmit function. To prevent possi-  
ble network faults, the host should clear the trans-  
mit buffer. Possible options include:  
3.9.3 Transmit Error Detection and Handling  
The MAC engine monitors Ethernet activity and  
reports and recovers from a number of error condi-  
tions. For transmission, the MAC reports the fol-  
lowing errors in the TxEvent register (Register 8)  
and BufEvent register (Register C):  
Reset the chip with either software or hardware re-  
set (see Section 3.3 on page 19).  
3.9.3.1 Loss of Carrier  
Issue a Force Transmit Command by setting the  
Force bit (Register 9, TxCMD, bit 8).  
Whenever the CS8900A is transmitting on the AUI  
port, it expects to see its own transmission "looped  
back" to its receiver. If it is unable to monitor its  
transmission after the end of the preamble, the  
MAC reports a loss-of-carrier error by setting the  
Loss-of-CRS bit (Register 8, TxEvent, Bit 6). If the  
Loss-of-CRSiE bit (Register 7, TxCFG, Bit 6) is  
set, the host will be interrupted.  
Issue a Transmit Command with the TxLength  
field set to zero.  
3.9.3.5 Transmit Collision  
The MAC counts the number of times an individual  
packet must be retransmitted due to network colli-  
sions. The collision count is stored in bits B  
through E of the TxEvent register (Register 8). If  
the packet collides 16 times, transmission of that  
packet is terminated and the 16coll bit (Register 8,  
TxEvent, Bit F) is set. If the 16colliE bit (Register  
7, TxCFG, Bit F) is set, the host will be interrupted  
on the 16th collision. A running count of transmit  
collisions is recorded in the TxCOL register.  
3.9.3.2 SQE Error  
After the end of transmission on the AUI port, the  
MAC expects to see a collision within 64 bit times.  
If no collision is detected, the SQEerror bit (Regis-  
ter 8, TxEvent, Bit 7) is set. If the SQEerroriE bit is  
set (Register 7, TxCFG, Bit 7), the host is interrupt-  
ed. An SQE error may indicate a fault on the AUI  
cable or a faulty transceiver (it is assumed that the  
attached transceiver supports this function).  
3.9.3.6 Transmit Underrun  
If the CS8900A starts transmission of a packet but  
runs out of data before reaching the end of frame,  
the TxUnderrun bit (Register C, BufEvent, Bit 9) is  
set. The MAC then forces a bad CRC and termi-  
nates the transmission. If the TxUnderruniE bit  
3.9.3.3 Out-of-Window (Late) Collision  
If a collision is detected after the first 512 bits have  
been transmitted, the MAC reports a late collision  
by setting the Out-of-window bit (Register 8, Tx-  
Event, Bit 9). The MAC then forces a bad CRC and  
terminates the transmission. If the Out-of-window-  
CIRRUS LOGIC PRODUCT DATA SHEET  
30  
DS271PP3