1.2.1. Debug access

You gain debug access in CoreSight systems using the Debug Access Port (DAP) that provides:

The same mechanism provides fast access for downloading code at the start of the debug session. This is faster than the traditional JTAG mechanism that uses the ARM core to write data to memory. You can still use the ARM core to write data to virtual memory and to ease migration when the debugger does not support this approach.

Figure 1.1 shows an example system with debug components and a DAP in a SoC design.

Figure 1.1. DAP connections inside a SoC

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The DAP provides the following advantages for multi-core SoC designs:

The DAP eases the physical implementation:

The DAP supports increased security to prevent unwanted debug activity:

For 100% backward compatibility with existing tools, you can serially daisy-chain JTAG scan chains with the DAP to provide access to them.

If you do this, you lose some of the advantages of the CoreSight Technology.

For more information on the DAP, see Debug Access Port.

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