TimeSerialPort » History » Version 1
laforge, 02/19/2016 10:49 PM
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1 | 1 | laforge | = The Time Serial Port (TSP = |
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3 | The TSP is a synchronous real-time control interface in TI GSM chipsets. |
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5 | The Digital Baseband (DBB) chip normally drives the TSP. The DBB has a special integrated peripheral unit called [wiki:TimeProcessingUnit TPU] to drive the TSP. |
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7 | The Baseband Codec and Transceiver chips are driven by the TSP (slaves) |
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9 | == Rationale == |
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11 | GSM is a synchronous TDMA system. As such, all clocks are related to each other, and all events driven synchronous to the master clock. |
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13 | The carrier clock determines the bit clock, which in turn determines the frame clock. |
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15 | When e.g. sending a GSM burst, a number of events have to happen synchronously to ensure transmitting it at the right instance in the TMDA sequence: |
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16 | * switching the RF-PA on |
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17 | * ramping up the power envelope |
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18 | * calibrating the DC offset |
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19 | * switching the MEMS antenna switch to the correct band |
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20 | * starting the transmit of the actual burst data |
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22 | To synchronize those events, and to schedule them in sequence before the burst is transmitted, the TSP is used. |
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24 | == Parallel vs. Serial == |
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26 | In early GSM transceivers, all the events could be driven by dedicated electrical lines from the TPU. |
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28 | However, in multi-band configurations and with integrated baseband codec circuits, it made more sense to |
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29 | have a serial interface to limit the number of signals that need to be routed between components. |
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31 | == TSP Signals == |
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33 | In the Calypso/Iota/Rita based modem designs, the TSP is only used uni-directional, i.e. from the DBB to the peripherals. |
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34 | Thus, only the following signals are needed: |
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35 | * TEN (TSP Enable), one for each peripheral |
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36 | * CLK13M - the 13MHz clocl that runs everywhere |
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37 | * TDX (TSP Data Tx) (used bi-directional for RF6151C) |