6.11 ATL Overview

The audio tracking logic (ATL) is used by HD Radio™ applications to synchronize the digital audio output to the baseband clock. This same IP can also be used generically to track errors between two reference signals (such as frame syncs) and generate a modulated clock output (using software-controlled cycle stealing) which averages to some desired frequency. This process can be used as a hardware assist for asynchronous sample rate conversion algorithms. The tracking range is limited, so direct conversion between the two standard sample rate groups frequencies from 44.1 to 48 kHz is not possible.

The ATL includes the following main features:

• One ATL module, containing four ATL instances, for HD Radio support and asynchronous sample rate conversion assistance
• Each instance tracks the time error between two syncs (local audio word select [AWS] and baseband word select [BWS])
• Each instance selects between 16 mux choices for each of AWS and BWS.
• Each instance generates modulated ATCLK_OUT clock signal with software-initiated pulse stealing.
• Selection between INTERCONNECT clock or functional ATLPCLK to run error couting timers and to derive modulated ATCLK_OUT clock outputs
• Clock and reset management: Receives clock and reset signals from the device PRCM module. The ATL module receives hardware reset from the CORE_RST reset domain.
• Power management: The ATL belongs to the PD_COREAON power domain.

For more information, see chapter Audio Tracking Logic of the Device TRM.