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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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FW802BF датащи(PDF) 3 Page - Agere Systems |
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FW802BF датащи(HTML) 3 Page - Agere Systems |
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3 / 26 page  Data Sheet FW802BF PHY 1394a-2000 January 2005 Two-Cable Transceiver/Arbiter Device Agere Systems Inc. 3 Description (continued) The PHY requires either an external 24.576 MHz crys- tal or crystal oscillator. The internal oscillator drives an internal phase-locked loop (PLL) that generates the required 393.216 MHz reference signal. The 393.216 MHz reference signal is internally divided to provide the 49.152 MHz, 98.304 MHz, and 196.608 MHz clock signals that control transmission of the outbound encoded strobe and data information. The 49.152 MHz clock signal is also supplied to the associated LLC for synchronization of the two chips and is used for resyn- chronization of the received data. The powerdown function, when enabled by the PD signal high, stops operation of the PLL and disables all circuitry except the cable-not-active (CNA) signal circuitry. The PHY supports an isolation barrier between itself and its LLC. When ISON is tied high, the link interface outputs behave normally. When ISON is tied low, inter- nal differentiating logic is enabled, and the outputs become short pulses that can be coupled through a capacitor or transformer as described in the IEEE 1394-1995 Annex J. To operate with bus-keeper isolation, the ISON ball of the FW802BF must be tied high. Data bits to be transmitted through the cable ports are received from the LLC on two, four, or eight data lines (D[0:7]), and are latched internally in the PHY in syn- chronization with the 49.152 MHz system clock. These bits are combined serially, encoded, and transmitted at 98.304 Mbits/s, 196.608 Mbits/s, or 393.216 Mbits/s as the outbound data-strobe information stream. During transmission, the encoded data information is transmit- ted differentially on the TPA and TPB cable pair(s). During packet reception, the TPA and TPB transmit- ters of the receiving cable port are disabled and the receivers for that port are enabled. The encoded data information is received on the TPA and TPB cable pair. The received data-strobe information is decoded to recover the receive clock signal and the serial data bits. The serial data bits are split into two (for S100), four (for S200), or eight (for S400) parallel streams, resynchronized to the local system clock, and sent to the associated LLC. The received data is also trans- mitted (repeated) out of the other active (connected) cable ports. Both the TPA and TPB cable interfaces incorporate differential comparators to monitor the line states dur- ing initialization and arbitration. The outputs of these comparators are used by the internal logic to deter- mine the arbitration status. The TPA channel monitors the incoming cable common-mode voltage. The value of this common-mode voltage is used during arbitra- tion to set the speed of the next packet transmission. In addition, the TPB channel monitors the incoming cable common-mode voltage for the presence of the remotely supplied twisted-pair bias voltage. This moni- tor is called bias-detect. The TPBIAS circuit monitors the value of incoming TPA pair common-mode voltage when local TPBIAS is inactive. Because this circuit has an internal current source and the connected node has a current sink, the monitored value indicates the cable connection status. This monitor is called connect-detect. Both the TPB bias-detect monitor and TPBIAS con- nect-detect monitor are used in suspend/resume signaling and cable connection detection. The PHY provides a 1.86 V nominal bias voltage for driver load termination. When seen through a cable by a remote receiver, this bias voltage indicates the pres- ence of an active connection. The value of this bias voltage has been chosen to allow interoperability between transceiver chips operating from 5 V or 3 V nominal supplies. This bias voltage source should be stabilized by using an external filter capacitor of approximately 0.33 µF. The transmitter circuitry, the receiver circuitry, and the twisted-pair bias voltage circuity are all disabled with a powerdown condition. The powerdown condition occurs when the PD input is high. The port transmitter circuitry, the receiver circuitry, and the TPBIAS output are also disabled when the port is disabled, sus- pended, or disconnected. The line drivers in the PHY operate in a high-imped- ance current mode and are designed to work with external 112 Ω line-termination resistor networks. One network is provided at each end of each twisted-pair cable. Each network is composed of a pair of series- connected 56 Ω resistors. The midpoint of the pair of resistors that is directly connected to the twisted-pair A (TPA) signals is connected to the TPBIAS voltage sig- nal. The midpoint of the pair of resistors that is directly connected to the twisted-pair B (TPB) signals is cou- pled to ground through a parallel RC network with recommended resistor and capacitor values of 5 k Ω and 220 pF, respectively. The value of the external resistors are specified to meet the IEEE 1394 stan- dard specifications when connected in parallel with the internal receiver circuits. The driver output current, along with other internal operating currents, is set by an external resistor. This resistor is connected between the R0 and R1 signals and has a value of 2.49 k Ω ± 1%. |
Аналогичный номер детали - FW802BF |
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Аналогичное описание - FW802BF |
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