CoreSight systems consist of a Debug Access Port (DAP) that comprises the following components:
A debug port (DP) that connects to the scan chain or Serial Wire Debug (SWD) interface, and that provides the system interface to debug hardware.
Either Advanced High-performance Bus Access Port (AHB-AP for AHB access) or ARM Peripheral Bus Access Port (APB-AP for APB access).
Debug components are attached to the buses, and are accessed through the APs on the DAP. CoreSight debug components are configured with the index of the AP to which they are attached, and the base address on the bus.
The DAP can also contain a JTAG-AP that enables the connection of JTAG devices on internal scan chains, for example ARM11 processors. JTAG devices must be configured with the AP index of the JTAG-AP, the JTAG port on the AP, and the pre-bits and post-bits for both IR and DR scans for the particular device.
CoreSight components are associated with a DAP, so they are placed on the scan chain (or SWD connection) after the DAP with which they are associated. The DAP is represented on the scan chain by the ARMCS-DP device. CoreSight components are not located on the JTAG scan chain, so they must be placed between the DAP and the next JTAG device.
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