Datasheet

374
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
28.9.9 Programming Enable Register
The Programming Enable Register is a 16-bit register. The contents of this register is compared to the
programming enable signature, binary code 0b1010_0011_0111_0000. When the contents of the register is
equal to the programming enable signature, programming via the JTAG port is enabled. The register is reset to
0 on Power-on Reset, and should always be reset when leaving Programming mode.
Figure 28-13. Programming Enable Register
28.9.10 Programming Command Register
The Programming Command Register is a 15-bit register. This register is used to serially shift in programming
commands, and to serially shift out the result of the previous command, if any. The JTAG Programming
Instruction Set is shown in Figure 28-15 on page 378. The state sequence when shifting in the programming
commands is illustrated in Figure 28-15 on page 378.
Figure 28-14. Programming Command Register
TDI
TDO
D
A
T
A
=
DQ
ClockDR & PROG_ENABLE
Programming Enable
0xA370
TDI
TDO
S
T
R
O
B
E
S
A
D
D
R
E
S
S
/
D
A
T
A
Flash
EEPROM
Fuses
Lock Bits