Rainbow Electronics ATmega128RFA1 - Manual (Page 484)

484
8266A-MCU Wireless-12/09
ATmega128RFA1
• Programming Enable Register
• Programming Command Register
• Flash Data Byte Register
31.9.8 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 148 ) after releasing the Reset Register.
The output from this Data Register is not latched, so the reset will take place
immediately, as shown in
"Figure 29-2" on page 443 .
31.9.9 Programming Enable Register
The Programming Enable Register is a 16-bit register. The content of this register is
compared to the programming enable signature, binary code 1010_0011_0111_0000.
When the content 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 31-17. Programming Enable Register
TDI
TDO
D
A
T
A
=
D Q
ClockDR & PROG_ENABLE
Programming Enable
0xA370
31.9.10 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
Table
31-18 on page 485. The state sequence when shifting in the programming commands
is illustrated in Figure 31-19 on page 488.