9.4.1 IR Codes
Table 9-3. JTAG Instructions
Instruction Code[3:0] Instruction Summary
IDCODE 0000 Selects device identification register for shift
SAMPLE/PRELOAD 0010 Selects boundary scan register for shifting, sampling, and
preloading without disturbing functional operation
SAMPLE 0011 Selects boundary scan register for shifting and sampling
without disturbing functional operation
EXTEST 0100 Selects boundary scan register while applying preloaded
values to output pins and asserting functional reset
HIGHZ 1001 Selects bypass register while three-stating all output pins and
asserting functional reset
CLAMP 1100 Selects bypass register while applying preloaded values to
output pins and asserting functional reset
EZPORT 1101 Enables the EZPORT function for the SoC and asserts
functional reset.
ARM_IDCODE 1110 ARM JTAG-DP Instruction
BYPASS 1111 Selects bypass register for data operations
Factory debug reserved 0101, 0110, 0111 Intended for factory debug only
ARM JTAG-DP Reserved 1000, 1010, 1011, 1110 These instructions will go the ARM JTAG-DP controller.
Please look at ARM JTAG-DP documentation for more
information on these instructions.
Reserved
3
All other opcodes Decoded to select bypass register
3. The manufacturer reserves the right to change the decoding of reserved instruction codes in the future
9.5 JTAG status and control registers
Through the ARM Debug Access Port (DAP), the debugger has access to the status and
control elements, implemented as registers on the DAP bus as shown in the following
figure. These registers provide additional control and status for low power mode recovery
and typical run-control scenarios. The status register bits also provide a means for the
debugger to get updated status of the core without having to initiate a bus transaction
across the crossbar switch, thus remaining less intrusive during a debug session.
It is important to note that these DAP control and status registers are not memory mapped
within the system memory map and are only accessible via the Debug Access Port (DAP)
using JTAG, cJTAG, or SWD. The MDM-AP is accessible as Debug Access Port 1 with
the available registers shown in the table below.
Table 9-4. MDM-AP Register Summary
Address Register Description
Table continues on the next page...
JTAG status and control registers
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
204 NXP Semiconductors
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