![](http://datasheet.mmic.net.cn/100000/IF180C52TXXX-20R_datasheet_3493957/IF180C52TXXX-20R_730.png)
730
32099I–01/2012
AT32UC3L016/32/64
31.4.5.1
I/O Lines
The TMS, TDI, TDO, and TCK pins are multiplexed with I/O lines. When the JTAG is used the
associated pins must be enabled. To enable the JTAG pins, refer to
Section 31.4.7.While using the multiplexed JTAG lines all normal peripheral activity on these lines is disabled.
The user must make sure that no external peripheral is blocking the JTAG lines while
debugging.
31.4.5.2
Power Management
When an instruction that accesses the SAB is loaded in the instruction register, before entering
a sleep mode, the system clocks are not switched off to allow debugging in sleep modes. This
can lead to a program behaving differently when debugging.
31.4.5.3
Clocks
The JTAG Interface uses the external TCK pin as clock source. This clock must be provided by
the JTAG master.
Instructions that use the SAB bus requires the internal main clock to be running.
31.4.6
JTAG Interface
The JTAG Interface is accessed through the dedicated JTAG pins shown in
Table 31-8 on pageThe TAP controller manages the serial access to the JTAG Instruction and Data registers. Data
is scanned into the selected instruction or data register on TDI, and out of the register on TDO,
in the Shift-IR and Shift-DR states, respectively. The LSB is shifted in and out first. TDO is high-
Z in other states than Shift-IR and Shift-DR.
The device implements a 5-bit Instruction Register (IR). A number of public JTAG instructions
defined by the JTAG standard are supported, as described in
Section 31.5.2, as well as a num-
ber of 32-bit AVR-specific private JTAG instructions described in
Section 31.5.3. Each
instruction selects a specific data register for the Shift-DR path, as described for each
instruction.