Motorola MCF5281 External Test Instruction Extest, Idcode Instruction, SAMPLE/PRELOAD Instruction

		Functional Description
	Table 31-5. JTAG Instructions (continued)
Instruction	IR[3:0]	Instruction Summary
TEST_LEAKAGE 1, 2	0101	Selects bypass register while tri-stating all output pins and assert to high the
		jtag_leakage signal
ENABLE_TEST_CTRL	0110	Selects TEST_CTRL register
HIGHZ	1001	Selects bypass register while tri-stating all output pins and asserting functional reset
LOCKOUT_RECOVERY	1011	Allows for the erase of the TFM flash when the part is secure
CLAMP	1100	Selects bypass while applying fixed values to output pins and asserting functional
		reset
BYPASS	1111	Selects bypass register for data operations
Reserved	all others	Decoded to select bypass register 3

1Instruction for manufacturing purposes only

2TRST pin assertion or power-on reset is required to exit this instruction.

3Motorola reserves the right to change the decoding of the unused opcodes in the future.

31.5.3.1 External Test Instruction (EXTEST)

The EXTEST instruction selects the boundary scan register. It forces all output pins and bidirectional pins configured as outputs to the values preloaded with the SAMPLE/PRELOAD instruction and held in the boundary scan update registers. EXTEST can also configure the direction of bidirectional pins and establish high-impedance states on some pins. EXTEST asserts internal reset for the MCU system logic to force a predictable internal state while performing external boundary scan operations.

31.5.3.2 IDCODE Instruction

The IDCODE instruction selects the 32-bit IDCODE register for connection as a shift path between the TDI and TDO pin. This instruction allows interrogation of the MCU to determine its version number and other part identification data. The shift register LSB is forced to logic 1 on the rising edge of TCLK following entry into the capture-DR state.Therefore, the first bit to be shifted out after selecting the IDCODE register is always a logic 1. The remaining 31 bits are also forced to fixed values on the rising edge of TCLK following entry into the capture-DR state.

IDCODE is the default instruction placed into the instruction register when the TAP resets. Thus, after a TAP reset, the IDCODE register is selected automatically.

31.5.3.3 SAMPLE/PRELOAD Instruction

The SAMPLE/PRELOAD instruction has two functions:

•SAMPLE - obtain a sample of the system data and control signals present at the MCU input pins and just before the boundary scan cell at the output pins. This sampling occurs on the rising edge of TCLK in the capture-DR state when the IR

MOTOROLA Chapter 31. IEEE 1149.1 Test Access Port (JTAG) 31-9