MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 795
32.8.4.2 ACCESS_AUX_TAP_x instructions
The ACCESS_AUX_TAP_x instructions allow the Nexus modules on the MCU to take control of the TAP.
When this instruction is loaded, control of the TAP pins is transferred to the selected auxiliary TAP
controller. Any data input via TDI and TMS is passed to the selected TAP controller, and any TDO output
from the selected TAP controller is sent back to the JTAGC to be output on the pins. The JTAGC regains
control of the JTAG port during the UPDATE-DR state if the PAUSE-DR state was entered. Auxiliary TAP
controllers are held in RUN-TEST/IDLE while they are inactive.
32.8.4.3 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
register using the SAMPLE/PRELOAD instruction before the selection of EXTEST. EXTEST asserts the
internal system reset for the MCU to force a predictable internal state while performing external boundary
scan operations.
32.8.4.4 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 is reset.
32.8.4.5 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.
During the SAMPLE instruction, the following pad status is enforced:
• Weak pull is disabled (independent from PCRx[WPE])
• Analog switch is disabled (independent of PCRx[APC])
• Slew rate control is forced to the slowest configuration (independent from PCRx[SRC[1]])
32.8.4.6 SAMPLE/PRELOAD instruction
The SAMPLE/PRELOAD instruction has two functions:
• The SAMPLE part of the instruction samples the system data and control signals on 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
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