Table 50-3. 4-bit JTAG instructions (continued)
Instruction
Code[3:0]
Instruction summary
ARM JTAG-DP Reserved
1011
This instruction goes the ARM JTAG-DP controller. See the
ARM JTAG-DP documentation for more information.
CLAMP
1100
Selects bypass register and applies preloaded values to
output pins.
NOTE: Execution of this instruction asserts functional reset.
EZPORT
1101
Enables the EZPORT function for the SoC
ARM JTAG-DP Reserved
1110
This instruction goes the ARM JTAG-DP controller. See the
ARM JTAG-DP documentation for more information.
BYPASS
1111
Selects bypass register for data operations
50.4.4.1 IDCODE instruction
IDCODE selects the 32-bit device identification register as the shift path between TDI
and TDO. This instruction allows interrogation of the MCU to determine its version
number and other part identification data. IDCODE is the instruction placed into the
instruction register when the JTAGC block is reset.
50.4.4.2 SAMPLE/PRELOAD instruction
The SAMPLE/PRELOAD instruction has two functions:
• The SAMPLE portion of the instruction obtains a sample of the system data and
control signals present at the MCU input pins and just before the boundary scan
register cells at the output pins. This sampling occurs on the rising edge of TCK in
the Capture-DR state when the SAMPLE/PRELOAD instruction is active. The
sampled data is viewed by shifting it through the boundary scan register to the TDO
output during the Shift-DR state. Both the data capture and the shift operation are
transparent to system operation.
• The PRELOAD portion of the instruction initializes the boundary scan register cells
before selecting the EXTEST or CLAMP instructions to perform boundary scan
tests. This is achieved by shifting in initialization data to the boundary scan register
during the Shift-DR state. The initialization data is transferred to the parallel outputs
of the boundary scan register cells on the falling edge of TCK in the Update-DR
state. The data is applied to the external output pins by the EXTEST or CLAMP
instruction. System operation is not affected.
Functional description
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
1308
Freescale Semiconductor, Inc.