Atmel SAM Approach » History » Version 1
laforge, 05/04/2018 09:54 PM
| 1 | 1 | laforge | h1. Atmel SAM Approach |
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| 3 | This page describes a proposed approach of implementing the E1 adapter using [[osmo-e1-xcvr]] and an Atmel SAMx microcontroller, suhc as a SAM3S or SAM4S. |
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| 5 | h2. Overview |
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| 7 | * the SAM controls the LIU via SPI |
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| 8 | * the SAM attaches to the host via USB |
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| 9 | * The SAM *SSC Peripheral* is used to interface to the receive + transmit bit-streams of the LIU |
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| 10 | * The SAM3 *TC Peripheral* is used for Rx frame alignment |
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| 12 | h2. Serializing/Deserializing |
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| 14 | * SSC can receive/transmit synchronous serial bit streams with external or internal clock |
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| 15 | * SSC supports DMA operation between the (de)serializer and RAM using PDC (peripheral DMA controller) |
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| 16 | * SSC can run either |
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| 17 | ** continously (frame alignment done in software [possibly using bit-banding], as no octet alignment of frames), or |
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| 18 | ** triggered by RF input, which we supply from SSC (see below) with hardware-assisted frame alignment |
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| 20 | h2. Frame Alignment using TC (Timer/Counter) |
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| 22 | The idea is to use one of the TC units to perform hardware-assisted frame alignment and this way prevent us from having to do tons of bit-shifting in software in order to align the start of the 256 bit E1 frame with an octet boundary. |
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| 24 | * received clock is fed into TCLKx |
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| 25 | * internal 16-bit counter is set to count up to 256 (one frame duration) |
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| 26 | * TC is operated in WAVEFORM mode |
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| 27 | * TIOA or TIOB are operated as output routed to the SSC RF (receive frame) input |
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| 28 | * Ra/Rb/Rc registers are used to shift the rising and falling edge of the TIOA/TIOB signal within the 256bit frame |
