參數資料
型號: AM79C970
廠商: Advanced Micro Devices, Inc.
英文描述: PCnetTM-PCI Single-Chip Ethernet Controller for PCI Local Bus
中文描述: PCnetTM - PCI單芯片以太網控制器的PCI總線
文件頁數: 160/168頁
文件大?。?/td> 943K
代理商: AM79C970
AMD
1-1027
Am79C970
The controller will discard all descriptors with
OWN = 1 and STP = 0 and move to the next de-
scriptor when searching for a place to begin a new
frame. It discards these descriptors by simply
changing the ownership bit from OWN=1 to OWN
= 0. Such a descriptor is unused for receive pur-
poses by the controller, and the driver must recog-
nize this. (Thedriver will recognize this if it follows
the software rules).
The controller will ignore all descriptors with OWN
= 0 and STP = 0 and move to the next descriptor
when searching for a place to begin a new frame.
In other words, the controller is allowed to skip en-
tries in the ring that it does not own, but only when
it is looking for a place to begin a new frame.
Some Examples of LAPP Descriptor
Interaction
Choose an expected frame size of 1060 bytes. Choose
buffer sizes of 800, 200 and 200 bytes.
Assume that a 1060 byte frame arrives correctly, and that the timing of the early interrupt and the software is
smooth. The descriptors will have changed from:
OWN
1
1
0
1
1
0
1
STP
1
0
0
1
0
0
1
ENP
X
X
X
X
X
X
X
OWN
0
0
0
1
1
0
1
STP
1
0
0
1
0
0
1
ENP
=
0
0
1
X
X
X
X
(after frame arrival)
bytes 1–800
bytes 801–1000
bytes 1001–1060
controller’s current location
not yet used
not yet used
not yet used
1
2
3
4
5
6
etc.
Descriptor
Number
Before the Frame Arrives
After the Frame has Arrived
Comments
=
ENP or ERR
Assume that instead of the expected 1060 byte frame, a 900 byte frame arrives, either because there was an
error in the network, or because this is the last frame in a file transmission sequence.
OWN
1
1
0
1
1
0
1
STP
1
0
0
1
0
0
1
ENP
X
X
X
X
X
X
X
OWN
0
0
0
1
1
0
1
STP
1
0
0
1
0
0
1
ENP
=
0
1
*
X
X
X
X
(after frame arrival)
bytes 1–800
bytes 801–900
discarded buffer
controller’s current location
not yet used
not yet used
not yet used
1
2
3
4
5
6
etc.
Descriptor
Number
Before the Frame Arrives
After the Frame has Arrived
Comments
=
ENP or ERR
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相關代理商/技術參數
參數描述
AM79C970A 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product
AM79C970AKC 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product
AM79C970AKC\\W 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Advanced Micro Devices 功能描述:
AM79C970AKC\W 制造商:Rochester Electronics LLC 功能描述:- Bulk