Rainbow Electronics ATmega162V - Manual (Page 252)

252
ATmega162/V
2513E–AVR–09/03
Data Registers The Data Registers are selected by the JTAG Instruction Registers described in section
“Programming Specific JTAG Instructions” on page 249. The Data Registers relevant for
programming operations are:
• Reset Register
• Programming Enable Register.
• Programming Command Register.
• Virtual Flash Page Load Register.
• Virtual Flash Page Read Register.
Reset Register The Reset Register is a test data register used to reset the part during programming. It
is required to reset the part before entering Programming mode.
A high value in the Reset Register corresponds to pulling the external reset low. The
part is reset as long as there is a high value present in the Reset Register. Depending
on the fuse settings for the clock options, the part will remain reset for a Reset Time-out
period (refer to “Clock Sources” on page 34) after releasing the Reset Register. The out-
put from this data register is not latched, so the reset will take place immediately, as
shown in Figure 86 on page 205.
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 1010_0011_0111_0000.
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 108. Programming Enable Register
TDI
TDO
D
A
T
A
=
D Q
ClockDR & PROG_ENABLE
Programming Enable
0xA370