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

The functionality of the library is separated into the following layers:

1. **Protocol Layer**: The protocol layer handles the binary packing and unpacking
   of data according to the protocol defined in the ICD for the Band 5 down-converter.
   The base class `BaseB5dcProtocol` implements the low-level packing/unpacking
   operations. `B5dcProtocol` implements the additional request/response routines to
   complete the protocol.

2. **Interface Layer**: The interface layer generate commands based on the interface 
   file (fpg) from reading and writing to registers. The register names and addresses
   are mapped to methods which are associated with the B5dcProtocol. The interface layer
   is implemented in `B5dcInterface` class. As an example, the interface class exposes
   the register ``spi_rfcm_frequency`` as a method ``set_spi_rfcm_frequency(val: int):`` 
   to set the register and a method ``spi_rfcm_frequency() -> int:`` to get the frequency
   from the device.

3. **Device Layer**: The device layer uses the `B5dcInterface` to configure the B5DC 
   and read the state of the device. This layer is implemented in `B5dcDevice` 
   class. It consists of: 

   * ``B5dcSensor(...)``: handles reading of useful state information.
   * ``B5dcDeviceConfigureAttenuation(...)``: handles setting of attenuation.
   * ``B5dcDeviceConfigureFrequency(...)``: handles setting of frequency.

The image below illustrates the connection between the classes.

.. image:: ../images/b5dc-design.png
    :width: 30%
    :align: center
    :alt: B5DC Design