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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  
4.5 Initiate Transmit Registers  
4.5.1 Transmit Command Request - TxCMD  
(Write-only, Address: PacketPage base + 0144h)  
7
6
5
4
3
2
1
0
TxStart  
001001  
F
E
D
C
B
A
9
8
TxPadDis  
InhibitCRC  
Onecoll  
Force  
The word written to PacketPage base + 0144h tells the CS8900A how the next packet should be transmitted. This  
PacketPage location is write-only, and the written word can be read from Register 9, at PacketPage base + 0108h.  
The CS8900A does not transmit a frame if TxLength (at PacketPage location base + 0146h) is less than 3. See  
Section 5.7 on page 99.  
001001  
These bits provide an internal address used by the CS8900A to identify this as the Transmit  
Command Register. When reading this register, these bits will be 001001, where the LSB cor-  
responds to Bit 0.  
TxStart  
This pair of bits determines how many bytes are transferred to the CS8900A before the MAC  
starts the packet transmit process.  
Bit 7 Bit 6  
0
0
1
1
0
1
0
Start transmission after 5 bytes are in the CS8900A  
Start transmission after 381 bytes are in the CS8900A  
Start transmission after 1021 bytes are in the CS8900A  
Start transmission after the entire frame is in the CS8900A  
1
Force  
When set in conjunction with a new transmit command, any transmit frames waiting in the trans-  
mit buffer are deleted. If a previous packet has started transmission, that packet is terminated  
within 64 bit times with a bad CRC.  
Onecoll  
When this bit is set, any transmission will be terminated after only one collision. When clear, the  
CS8900A allows up to 16 normal collisions before terminating the transmission.  
InhibitCRC  
TxPadDis  
When set, the CRC is not appended to the transmission.  
When TxPadDis is clear, if the host gives a transmit length less than 60 bytes and InhibitCRC  
is set, then the CS8900A pads to 60 bytes. If the host gives a transmit length less than 60 bytes  
and InhibitCRC is clear, then the CS8900A pads to 60 bytes and appends the CRC.  
When TxPadDis is set, the CS8900A allows the transmission of runt frames (a frame less than  
64 bytes). If InhibitCRC is clear, the CS8900A appends the CRC. If InhibitCRC is set, the  
CS8900A does not append the CRC.  
Since this register is write-only, it’s initial state after reset is undefined.  
4.5.2 Transmit Length  
(Write-only, Address: PacketPage base + 0146h)  
Address 0147h  
Most-significant byte of Transmit Frame Length  
Address 0146h  
Least-significant byte of Transmit Frame Length  
This register is used in conjunction with register 9, TxCMD. When a transmission is initiated via a command in Tx-  
CMD, the the length of the transmitted frame is written into this register. The length of the transmitted frame may be  
modified by the configuration of the TxPadDis and InhibitCRC bits in the TxCMD register. See Table 35, and  
Section 5.7 on page 99. TxLength must be >3 and < 1519.  
Since this register is write-only, it’s initial state after reset is undefined.  
CIRRUS LOGIC PRODUCT DATA SHEET  
DS271PP3  
71  
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