reorder_transpose.vhd

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--
-- Copyright (C) 2011
-- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/>
-- JIVE (Joint Institute for VLBI in Europe) <http://www.jive.nl/>
-- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
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-- Purpose: Performing a transpose (reordering data) on one or more streaming 
--          inputs using external memory.
--
-- Description:
--   The input of multiple streams (g_nof_streams) is concatenated into a 
--   single stream. Either the data field or the complex fields can be 
--   used, based on the g_use_complex generic.
-- 
--   Data on this single stream is than transposed according to the settings 
--   of g_frame_size_in and g_reorder_seq. 
--   The actual transpose is divided in two stages. The first stage (pre_transpose) 
--   is done using a subband select module (reorder_col in RadioHDL).
--   The second stage is done in external memory (DDR3, DDR4,...). 
--  
--   Stage 1: Pre Transpose 
--   This stage is used to reorder data with a resolution as high as a single 
--   sample, because the second stage (if using DDR3 for instance) has a resolution
--   of 16 or more samples. The ss_ss_transp mm interface can be used to specify
--   the desired reordering for the pre transpose. 
--
--   Stage 2: Reorder Sequencer
--   After the pre transpose the data is send to the external memory 
--   interface (to_mem_src_out). The reorder sequencer module provides the address
--   and control signals for the external memory. Writing and reading is done in a 
--   alternating way. Data from the external memory is received via the 
--   from_mem_snk_in interface. The sequencers rhythm is based on the settings of 
--   the g_reorder_seq generic.  
-- 
--   At the output the data from the single stream is split up in the original 
--   g_nof_streams again. A block_gen module is used to generate the SYNC, SOP and EOP 
--   signals. 
--  
--   SYNC and BSN
--   At the input the BSN number at every SYNC is written to a fifo. This BSN number
--   is inserted in the output data again when a SYNC is applied at the output. 
-- 
--   SYNC Period
--   The SYNC period (the number of blocks per sync interval) is monitored with a counter.
--   In case the number of blocks within a syncperiod is not equal to the specified 
--   g_reorder_seq.nof_blocks the sequencer will reset and start again when the number of 
--   received blocksdoes match the g_reorder_seq.nof_blocks. 
--
--   Complex or real data:
--   The the width of snk_in.data, re, im is g_in_dat_w. When g_use_complex = FALSE then
--   snk_in.data is passed on internally, so then the internal sosi.data width is also
--   g_in_dat_w. When g_use_complex = TRUE then snk_in.im and snk_in.re are concatenated
--   into an internal sosi.data that has then width 2*g_in_dat_w. The g_nof_streams are
--   also concatenated into the sosi.data.