Specifications

ARM Debugger 60 ARM specific SYStem Commands
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<parameter> configuring a CoreSight Debug Access Port “DAP”
A Debug Access Port (DAP) is a CoreSight module from ARM which provides access via its debugport
(JTAG, cJTAG, SWD) to:
1. Different memory busses (AHB, APB, AXI). This is especially important if the on-chip debug register
needs to be accessed this way. You can access the memory buses by using certain access classes with the
debugger commands: “AHB:”, “APB:”, “AXI:, “DAP”, “E:”. The interface to these buses is called Memory
Access Port (MEM-AP).
2. Other, chip-internal JTAG interfaces. This is especially important if the core you intend to debug is
connected to such an internal JTAG interface. The module controlling these JTAG interfaces is called JTAG
Access Port (JTAG-AP). Each JTAG-AP can control up to 8 internal JTAG interfaces. A port number between
0 and 7 denotes the JTAG interfaces to be addressed.
3. At emulation or simulation system with using bus transactors the access to the busses must be specified
by using the transactor identification name instead using the access port commands. For emulations/
simulations with a DAP transactor the individual bus transactor name don’t need to be configured. Instead of
this the DAP transactor name need to be passed and the regular access ports to the busses.