Datasheet
73
42023E–SAM–07/2013
ATSAM4L8/L4/L2
8.7.14 JTAG Instructions
Refer to the ARM Debug Interface v5.1 Architecture Specification for more details on ABORT,
DPACC, APACC and IDCODE instructions.
8.7.14.1 EXTEST
This instruction selects the boundary-scan chain as Data Register for testing circuitry external to
the chip package. The contents of the latched outputs of the boundary-scan chain is driven out
as soon as the JTAG IR-register is loaded with the EXTEST instruction.
Starting in Run-Test/Idle, the EXTEST instruction is accessed the following way:
1. Select the IR Scan path.
2. In Capture-IR: The IR output value is latched into the shift register.
3. In Shift-IR: The instruction register is shifted by the TCK input.
4. In Update-IR: The data from the boundary-scan chain is applied to the output pins.
5. Return to Run-Test/Idle.
6. Select the DR Scan path.
7. In Capture-DR: The data on the external pins is sampled into the boundary-scan chain.
8. In Shift-DR: The boundary-scan chain is shifted by the TCK input.
9. In Update-DR: The data from the scan chain is applied to the output pins.
10. Return to Run-Test/Idle.
8.7.14.2 SAMPLE_PRELOAD
This instruction takes a snap-shot of the input/output pins without affecting the system operation,
and pre-loading the scan chain without updating the DR-latch. The boundary-scan chain is
selected as Data Register.
Starting in Run-Test/Idle, the Device Identification register is accessed in the following way:
DR Size
Shows the number of bits in the data register chain when this instruction is active.
Example: 32 bits
DR input value
Shows which bit pattern to shift into the data register in the Shift-DR state when this
instruction is active.
DR output value
Shows the bit pattern shifted out of the data register in the Shift-DR state when this
instruction is active.
Table 8-4. Instruction Description (Continued)
Instruction Description
Table 8-5. EXTEST Details
Instructions Details
IR input value 0000 (0x0)
IR output value p00s
DR Size Depending on boundary-scan chain, see BSDL-file.
DR input value Depending on boundary-scan chain, see BSDL-file.
DR output value Depending on boundary-scan chain, see BSDL-file.