ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 268

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

25.4
25.5
25.6
25.6.1
268
Software Break Points
Limitations of debugWIRE
Register Description
Atmel ATmega48PA/88PA/168PA [Preliminary]
DWDR – debugWire Data Register
When designing a system where debugWIRE will be used, the following observations must be
made for correct operation:
• Pull-up resistors on the dW/(RESET) line must not be smaller than 10k . The pull-up resistor
• Connecting the RESET pin directly to V
• Capacitors connected to the RESET pin must be disconnected when using debugWire.
• All external reset sources must be disconnected.
debugWIRE supports Program memory Break Points by the AVR Break instruction. Setting a
Break Point in AVR Studio
instruction replaced by the BREAK instruction will be stored. When program execution is con-
tinued, the stored instruction will be executed before continuing from the Program memory. A
break can be inserted manually by putting the BREAK instruction in the program.
The Flash must be re-programmed each time a Break Point is changed. This is automatically
handled by AVR Studio through the debugWIRE interface. The use of Break Points will there-
fore reduce the Flash Data retention. Devices used for debugging purposes should not be
shipped to end customers.
The debugWIRE communication pin (dW) is physically located on the same pin as External
Reset (RESET). An External Reset source is therefore not supported when the debugWIRE is
enabled.
A programmed DWEN Fuse enables some parts of the clock system to be running in all sleep
modes. This will increase the power consumption while in sleep. Thus, the DWEN Fuse
should be disabled when debugWire is not used.
The following section describes the registers used with the debugWire.
The DWDR Register provides a communication channel from the running program in the MCU
to the debugger. This register is only accessible by the debugWIRE and can therefore not be
used as a general purpose register in the normal operations.
Bit
Read/Write
Initial Value
is not required for debugWIRE functionality.
R/W
7
0
R/W
6
0
®
will insert a BREAK instruction in the Program memory. The
R/W
5
0
CC
R/W
4
0
will not work.
DWDR[7:0]
R/W
3
0
R/W
2
0
R/W
1
0
R/W
0
0
9223B–AVR–09/11
DWDR