.. _fsp_corr_design_overview:

Design Overview
===============

Introduction
------------

This page will summarize and provide a design overview of the Frequency Slice Processor (FSP) Correlation (CORR) component of the Mid Telescope Correlator and Beamformer. 
Included is an overview of the software, a diagram of the architecture and context, and a sequence diagram for one of the commands.
This page is intended for System Engineers and other members of the CBF team wanting to understand the FSP Corr design at a high level.


Overview
--------
The FSP CORR software monitor and control is an internal component of the FSP Corr software. 
FSP-CORR exposes a set of Tango commands, attributes and properties to the monitor and control software (MCS) which it uses both to perform scan operations 
as well as monitor the states of the various subarrays using the FSP and their relevant devices.

When in CORR mode, each FSP FPGA board is responsible for taking 200 MHz
Frequency Slice (FS) inputs provided by VCC and generating cross-correlated output
visibilities to be sent to the SDP. A maximum of 24 input VCCs are supported
simultaneously, spread across up to 16 independent subarrays. FSP-CORR exposes an
interface to MCS providing commands to start, stop, and configure a scan for a
particular subarray, among others.


FSP CORR Software Diagrams
--------------------------
.. image:: ../diagrams/fsp-corr/software_architecture/fsp_corr_sw_architecture.png
    :alt: FSP CORR Software Architecture diagram
    :scale: 100%
    :align: center

The FSP CORR hierarchy shows how commands move from the control system MCS down to the hardware.
At the top, the MCS sends instructions that are handled by Tango controller device servers in the CORR software.
The high level servers translate the commands and work with lower level Tango components that manage more detailed configuration and control.
The firmware layer then passes these instructions to the FPGA where the actual correlation takes place.

.. image:: ../diagrams/fsp-corr/software_architecture/fsp_corr_software_context_diagram.png
    :alt: FSP CORR Software Context diagram
    :scale: 100%
    :align: center

The figure above provides a general overview of the FSP-CORR software in context with the FHS, FPGAs, and Kubernetes node.


Sequence Diagrams
-----------------

ConfigureScan
~~~~~~~~~~~~~
.. figure:: ../diagrams/fsp-corr/commands/svg/ConfigureScan.svg
    :alt: ConfigureScan sequence diagram
    :width: 100%
    :align: center

    Sequence diagram for ConfigureScan