IEEE 1149.1 Test Access Port Controller (JTAGC)
MPC5606S Microcontroller Reference Manual, Rev. 7
724 Freescale Semiconductor
19.8.4.1 BYPASS instruction
BYPASS selects the bypass register, creating a single-bit shift register path between TDI and TDO.
BYPASS enhances test efficiency by reducing the overall shift path when no test operation of the MCU is
required. This allows more rapid movement of test data to and from other components on a board that are
required to perform test functions. While the BYPASS instruction is active the system logic operates
normally.
19.8.4.2 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.
19.8.4.3 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
Table 19-4. JTAG instructions for silicon cut1
Instruction Code[4:0] Instruction summary
IDCODE 00001 Selects device identification register for shift
SAMPLE/PRELOAD 00010 Selects boundary scan register for shifting, sampling, and preloading without
disturbing functional operation
SAMPLE 00011 Selects boundary scan register for shifting and sampling without disturbing
functional operation
EXTEST 00100 Selects boundary scan register while applying preloaded values to output
pins and asserting functional reset
ACCESS_AUX_TAP_TCU 10000 Grants the TCU ownership of the TAP
ACCESS_AUX_TAP_ONCE 10001 Grants the PLATFORM ownership of the TAP
ACCESS_AUX_TAP_NPC 10010 Grants the Nexus port controller (NPC) ownership of the TAP
BYPASS 11111 Selects bypass register for data operations
Factory Debug Reserved
1
1
Intended for factory debug, and not customer use
00101
00110
01010
Intended for factory debug only
Reserved
2
2
Freescale reserves the right to change the decoding of reserved instruction codes
All Other Codes Decoded to select bypass register
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