Rainbow Electronics Atmega169L - Manual (Page 286)

286
ATmega169V/L
2514A–AVR–08/02
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 24) 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 107 on page 233.
Programming Enable Register The Programming Enable Register is a 16-bit register. The contents of this register is
c o m p a r e d
t o t h e p r o g r a m m i n g e n a b l e s i g n a t u r e , b i n a r y c o d e
0b1010_0011_0111_0000. When the contents of the register is equal to the program-
ming 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 131. Programming Enable Register
TDI
TDO
D
A
T
A
=
D Q
ClockDR & PROG_ENABLE
Programming Enable
0xA370