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laforge, 05/04/2018 09:56 PM
add data sheets
Atmel SAM Approach¶
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.
- SAM4S Manual (64 MHz Cortex-M3)
- SAM4S Manual (120 MHz Cortex-M4)
Overview¶
- the SAM controls the LIU via SPI
- the SAM attaches to the host via USB
- The SAM SSC Peripheral is used to interface to the receive + transmit bit-streams of the LIU
- The SAM3 TC Peripheral is used for Rx frame alignment
Serializing/Deserializing¶
- SSC can receive/transmit synchronous serial bit streams with external or internal clock
- SSC supports DMA operation between the (de)serializer and RAM using PDC (peripheral DMA controller)
- SSC can run either
- continously (frame alignment done in software [possibly using bit-banding], as no octet alignment of frames), or
- triggered by RF input, which we supply from SSC (see below) with hardware-assisted frame alignment
Frame Alignment using TC (Timer/Counter)¶
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.
- received clock is fed into TCLKx
- internal 16-bit counter is set to count up to 256 (one frame duration)
- TC is operated in WAVEFORM mode
- TIOA or TIOB are operated as output routed to the SSC RF (receive frame) input
- Ra/Rb/Rc registers are used to shift the rising and falling edge of the TIOA/TIOB signal within the 256bit frame
Updated by laforge about 6 years ago · 2 revisions