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AM79C988A 数据表(PDF) 9 Page - Advanced Micro Devices |
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AM79C988A 数据表(HTML) 9 Page - Advanced Micro Devices |
9 / 25 page Am79C988A 9 PRELIMINARY PAUI Ports The PAUI ports are functionally equivalent to AUI ports as described in IEEE 802.3, Section 7. However, they are single ended and, therefore, are not an exact match with the electrical specifications. PDO, PDI, and PCI are functionally similar to DO, DI, and CI, respectively. PDO is the PAUI input from the IMR2 device. This signal is transmitted by the corre- sponding TXD port. PDI is the data output to the IMR2 device and is the data received by the corresponding RXD port. PDI also loops back data received by PDO to the IMR2 device. PCI is the collision output to the IMR2 device and indicates either a collision on the cor- responding port or an excessive continuous data stream on the corresponding PDO. PCI sends a 10-MHz square wave during collision and jabber. Collision Handling Collision is defined for the QuIET device as data being simultaneously transmitted and received at the corre- sponding TXD and RXD pins. When a collision is de- tected, the QuIET device sends a 10 MHz signal over the corresponding PCI pin. This is the only action taken by the QuIET device. The generation of the JAM signal is performed by the IMR2 device. Jabber Protection The Jabber function inhibits the twisted pair transmit function of the port if the PDO circuit is active for an excessive period (> 30 ms). If the maximum transmit time is exceeded, the transmitter circuitry is disabled, PDO to PDI loopback is disabled, and a 10 MHz signal is transmitted by PCI. Once the data stream is removed from PDO, 350 ms will elapse before PCI stops trans- mitting the 10 MHz signal and the TXD circuitry is en- abled again. Note that a properly functioning repeater device will never jabber because of the MAU Jabber Lockup Protection (MJLP). Transceiver Modes The QuIET transceivers have two modes of operation: Normal and Full Duplex. In Normal mode, the data flows only in one direction at a time. In Full-Duplex mode, the collision circuitry and the loopback circuitry are dis- abled. Therefore, transmit and receive can occur simul- taneously.The transceiver mode is selected through the serial management interface, which is explained further in the Management Commands and Transceiver Mode Selection sections. Normal Mode The QuIET device defaults to the Normal mode at power up and reset. In this mode, no twisted pair port can transmit and receive data simultaneously. If a port re- ceives data when it is transmitting, the QuIET device sends a collision signal to the IMR2 device via the cor- responding PCI pin. Note: The IMR2 device only supports Normal operation. Full-Duplex Mode In Full-Duplex mode a port can transmit and receive simul- taneously, and Collision and PAUI Loopback functions are disabled. The normal loopback of PDO to PDI is disabled to allow the RXD signal to be transmitted on PDI. PCI is disabled and Jabber status is only available to the controller through the serial management interface. The serial management interface also transmits Jabber status when the QuIET device is in Normal mode. Serial Management Interface Command and status data are transferred between the QuIET device and the IMR2 device via SDATA. (See Figure 4 for proper interconnections.) The direction of SDATA is set by DIR. All activity on SDATA starts at the edge (rising or falling) of DIR. The DIR pin of the QuIET device connects to DIR[1] of the IMR2 device. The IMR2 device continually cycles DIR[1] LOW and HIGH. LOW is status reporting (SDATA Write) and HIGH is management commands (SDATA Read). The controller (IMR2 device) should keep DIR at one level for the entire bit stream. The status bit stream is described in the Status Reporting section, and the command bit stream is described in the Manage- ment Commands section. Each bit on SDATA is held for 2-bit times (200 ns). Status Reporting When DIR switches from HIGH to LOW, the QuIET de- vice drives SDATA with status information (left to right) in the format shown below. After the 29th bit, the SDATA driver turns off. The SDATA driver also turns off if DIR switches HIGH before the 29th bit. Status Information Format 01010A0A1A2A3B0B1B2B3C0C1C2C3D0D1D2D3SSSSSSSS Preamble The 01010 preamble is an indication to the IMR2 that the transceiver is a QuIET device. QuIET Device ID A0A1A2A3 The QuIET device returns 0000. 01010 Preamble An QuIET device ID (0000 for QuIET device) Bn 0 Link Fail 1 Link Pass Cn 0 Received Polarity Reversed 1 Received Polarity Correct Dn 0 No Jabber 1 Jabber S Not used, logic HIGH |
类似零件编号 - AM79C988A |
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类似说明 - AM79C988A |
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