Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 317
Register. The output from this Data Register is not latched, so the reset will take place immediately, as shown in
Figure 25-2 on page 270.
27.10.9 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 27-14. Programming enable register
27.10.10Programming 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 Table 27-18 on page 318. The state sequence when shifting in the programming
commands is illustrated in Figure 27-16 on page 321.
Figure 27-15. 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