Datasheet

372
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
Figure 28-12. State Machine Sequence for Changing the Instruction Word
28.9.2 AVR_RESET (0xC)
The AVR specific public JTAG instruction for setting the AVR device in the Reset mode or taking the device out
from the Reset mode. The TAP controller is not reset by this instruction. The one bit Reset Register is selected
as Data Register. Note that the reset will be active as long as there is a logic “one” in the Reset Chain. The
output from this chain is not latched.
The active states are:
 Shift-DR: The Reset Register is shifted by the TCK input.
28.9.3 PROG_ENABLE (0x4)
The AVR specific public JTAG instruction for enabling programming via the JTAG port. The 16-bit Programming
Enable Register is selected as Data Register. The active states are the following:
 Shift-DR: The programming enable signature is shifted into the Data Register
 Update-DR: The programming enable signature is compared to the correct value, and Programming
mode is entered if the signature is valid
28.9.4 PROG_COMMANDS (0x5)
The AVR specific public JTAG instruction for entering programming commands via the JTAG port. The 15-bit
Programming Command Register is selected as Data Register. The active states are the following:
Test-Logic-Reset
Run-Test/Idle
Shift-DR
Exit1-DR
Pause-DR
Exit2-DR
Update-DR
Select-IR Scan
Capture-IR
Shift-IR
Exit1-IR
Pause-IR
Exit2-IR
Update-IR
Select-DR Scan
Capture-DR
0
1
0
11 1
00
00
11
1
0
1
1
0
1
0
0
1
0
1
1
0
1
0
0
00
11