PXS20RM Datasheet, PDF (951/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

JTAG Controller (JTAGC)
Table 29-3. JTAG Instructions (continued)
Instruction
Code[4:0]
Instruction Summary
ACCESS_AUX_TAP_MULTI
BYPASS
Reserved¹
11100
11111
All other opcodes
Enables access to and serializes the Core_0 and Core_1
TAPs
Selects bypass register for data operations
Decoded to select bypass register
NOTES:
1 _{The manufacturer reserves the right to change the decoding of reserved instruction codes in the future}
29.4.4.1 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.
29.4.4.2 SAMPLE/PRELOAD Instruction
The SAMPLE/PRELOAD instruction has two functions:
• First, 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.
• Secondly, the PRELOAD portion of the instruction initializes the boundary scan register cells
before selecting the EXTEST instruction 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 instruction. System operation is not affected.
29.4.4.3 SAMPLE Instruction
The SAMPLE 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 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. There is no
defined action in the Update-DR state. Both the data capture and the shift operation are transparent to
system operation.
29.4.4.4 EXTEST — External Test Instruction
EXTEST selects the boundary scan register as the shift path between TDI and TDO. It allows testing of
off-chip circuitry and board-level interconnections by driving preloaded data contained in the boundary
scan register onto the system output pins. Typically, the preloaded data is loaded into the boundary scan
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
29-11