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Chapter 3 |
| Hardware | ||
Table | ||||
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| 1 | TX+ | Analog Twisted Pair Ethernet Transmit Differential Pair. These pins transmit the |
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| serial bit stream for transmission on the Unshielded Twisted Pair Cable (UTP). |
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| 2 | TX- | ||
| These signals interface directly with an isolation transformer. |
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| 3 | RX | Analog Twisted Pair Ethernet Receive Differential Pair. These pins receive the |
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| serial bit stream from the isolation transformer. |
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| 6 | RX- | ||
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| 4, 5 | Term | Termination |
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| 7, 8 | Term | Termination |
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| 9 | Speed | Speed signals (10BaseT or 100BaseT transfer rate) to green LED |
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| 10 | 3.3V | +3.3 volts +/- 5% |
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| 11 | Link | Link signals for yellow LED |
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| 12 | Activity | Activity signals for yellow LED |
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| 13, 14 | Shld | Grounded Shield |
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Note: Termination involves connecting a 75 ohm resistor between the connector and a capacitance plane created on an inner layer power plane.
Audio Interface (J28)
The audio solution on the LittleBoard 550 is provided by the VT82C686B and the LM4549 audio CODEC. These two chips use a digital interface to communicate between the two, which is defined by AC97 and is revision 2.1 compliant. The LittleBoard 550 supports its own audio amplifier (LM4853), which drives the audio signals into an external audio load. Output signals for the audio interface are through the
Audio CODEC (LM4549) features
•Analog Mixer Dynamic Range 97dB (typ)
•D/A Dynamic Range 89dB (typ)
•A/D Dynamic Range 90dB (typ)
•AC’97 Rev 2.1 compliant
•3D Sound circuitry
•High quality Sample Rate Conversion (SRC) from 4kHz to 48kHz
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•True Line Level Output with volume control independent of Line Out Audio Amplifier (LM4853) features
•Dual
•2.2W into 4Ω load or 1.1W into 8Ω load.
•Dual Bridge speaker amplifiers
•Stereo headphone amplifier
•External Audio Interface
LittleBoard 550 | Reference Manual | 53 |