Rainbow Electronics ATmega128L - Manual (Page 300)

300
ATmega128(L)
2467B–09/01
When the contents of the register is equal to the programming enable signature, pro-
gramming 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 147. Programming Enable Register
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 com-
mand, if any. The JTAG Programming Instruction Set is shown in
Table 132. The state
sequence when shifting in the programming commands is illustrated in Figure 149.
TDI
TDO
D
A
T
A
=
D Q
ClockDR & PROG_ENABLE
Programming enable
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