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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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AM79C970A датащи(PDF) 210 Page - Advanced Micro Devices |
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AM79C970A датащи(HTML) 210 Page - Advanced Micro Devices |
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210 / 219 page  AMD D-6 Am79C970A 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 purposes by the controller, and the driver must recognize this. (The driver 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 al- lowed to skip entries 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 STP ENP ¦ OWN STP ENP ¦ (After frame arrival) 1 1 1 X 0 1 0 Bytes 1–800 2 1 0 X 0 0 0 Bytes 801–1000 3 0 0 X 0 0 1 Bytes 1001–1060 4 1 1 X 1 1 X Controller’s current location 5 1 0 X 1 0 X Not yet used 6 0 0 X 0 0 X Not yet used etc. 1 1 X 1 1 X Not yet used 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 STP ENP ¦ OWN STP ENP ¦ (After frame arrival) 1 1 1 X 0 1 0 Bytes 1–800 2 1 0 X 0 0 1 Bytes 801–900 3 0 0 X 0 0 ?* Discarded buffer 4 1 1 X 1 1 X Controller’s current location 5 1 0 X 1 0 X Not yet used 6 0 0 X 0 0 X Not yet used etc. 1 1 X 1 1 X Not yet used Descriptor Number Before the Frame Arrives After the Frame has Arrived Comments ¦ ENP or ERR |
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