Introduction
************

The purpose of this document is to describe the Texas Instruments Inc. (TI)
vendor specific Host Controller Interface (HCI) for Bluetooth® low energy (BLE).

Functional Overview
===================

In BLE, there is a logical distinction between the Host software (often referred
to as the higher layer stack) and the Controller software as shown below.

.. _stack-layers:
.. figure:: resources/stack-layers.png
    :align: center

    BLE Protocol Stack Layers

These components can either exist on the same device (single-device
configuration), or be placed on separate devices (dual-device configuration)
utilizing a Host Controller Interface (HCI) for communication. In the single-device configuration, 
there is obviously only one device, and the application software would execute on top of the BLE profiles
and stack.

.. _single-device:
.. figure:: resources/single-device.png
    :align: center

    Single Device Configuration

In the dual-device configuration, the application software would also execute
on top of the BLE profiles and stack, and only the controller would be located
on a separate device.

.. _dual-device:
.. figure:: resources/dual-device.png
    :align: center

    Dual Device Configuration

Numerical Notation Conventions
==============================

Multiple-octets may be specified in hexadecimal notation in one of two ways:

Standard Hexadecimal Notation
-----------------------------

In this notation, a single hexadecimal radix indicator “0x” precedes the entire
value. The octet order as read from left to right is from most significant octet
to least significant octet. For example, for the value 0x123456ABCDEF, ’12’ is
the most significant octet and ‘EF’ is the least significant octet.

Colon Separated Hexadecimal Notation
------------------------------------

In this notation, the hexadecimal radix indicator “0x” is not used and octets
are colon separated. The octet order as read from left to right is from least
significant octet to most significant octet. For example, for the value
12:34:56:AB:CD:EF, ’12’ is the least significant octet and ‘EF’ is the most
significant octet.