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IDT77105 Datasheet(PDF) 12 Page - Integrated Device Technology |
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IDT77105 Datasheet(HTML) 12 Page - Integrated Device Technology |
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12 / 24 page  12 of 24 September 11, 2000 IDT77105 This leaves the interrupt system ready to signal an alarm for further problems. Cable Disconnect Procedures and Link Cable Disconnect Procedures and Link Cable Disconnect Procedures and Link Cable Disconnect Procedures and Link Establishment Establishment Establishment Establishment During the initial state of connecting the line for IDT77105, there are some interrupts (“HEC Error Cell Received” interrupt, “Short Cell Received” interrupt, and “Received Cell Symbol Error” interrupt) that may appear. These interrupts should be masked. When the line is disconnected, these interrupts may also appear, but this depends on the passive network between the magnetics and the 77105. Previous network recommendations did not adequately address this matter, the result being that the receiver would generate needless repetitive interrupts. The latest network recommendations, shown in Figure 21, pull the RXD+ and RXD- inputs to different D.C. voltages in the absence of a signal. This prevents false receive signals when there is no actual signal, and thus prevent repetitive interrupts. Register Status for Established Link Register Status for Established Link Register Status for Established Link Register Status for Established Link IDT77105 register setting and status are as follows when the link condition exists. LED Control and Signalling LED Control and Signalling LED Control and Signalling LED Control and Signalling The LED outputs, pins 13 and 14 provide bi-directional LED drive capability of 10mA. As an example, the RxLED pin’s output is described in the truth table: As illustrated in the following drawing (Figure 8), this could be connected to provide for a two-LED condition indicator. These could also be different colors to provide simple status indication at a glance. (The value of R is determined to limit LED current to 10mA or less as speci- fied by the LED manufacturer. Minimum value for R should be 270 Ω). TxLED Truth Table (Pin 14) TxLED Truth Table (Pin 14) TxLED Truth Table (Pin 14) TxLED Truth Table (Pin 14) Master Control Register 0x00 contents => 49h Interrupt Status Register 0x01 contents => 40h Diagnostic Control Register 0x02 contents => 00h State Pin Voltage Cell being received Low Cells not being received High State Pin Voltage Cell being transmitted Low Cells not being transmitted High Figure 8 Diagnostic Functions Diagnostic Functions Diagnostic Functions Diagnostic Functions 1. Loopback 1. Loopback 1. Loopback 1. Loopback There are two loopback modes supported by the 77105. The loop- back mode is controlled via Register 0x02, bits 1 and 0: Normal Mode This mode, Figure 9, supports normal operating conditions: data to be transmitted is transferred to the TC, where it is queued and formatted for transmission by the PMD. Receive data from the PMD is decoded along with its clock for transfer to the receiving "upstream system". PHY Loopback As Figure 10 illustrates below, this loopback mode provides a connection within the PHY between transmit and receive data. Note that while this mode is operating, no data is forwarded to or received from the line interface. Line Loopback Figure 11 might also be called “remote loopback” since it provides for a means to test the overall system, including the line. Since this mode will probably be entered under direction from another system (at a remote location), receive data is also decoded and transferred to the upstream system to allow it to listen for commands. A common example would be a command asking the upstream system to direct the TC to leave this loopback state, and resume normal operations. Entering Loopback (Byte Mode) In byte mode, the 77105 counts 53 bytes after each TxSOC, and after receiving a complete cell, the cell is transmitted. 0x02 Bit 1 Bit 0 0 0 Normal operating mode 1 0 PHY Loopback 1 1 Line Loopback RxLED, Pin 13 Vcc (Indicates: Cells being received) (Indicates: Cells are not being received) 3445 drw 11 R R |
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