ATMEGA88-20AJ Atmel, ATMEGA88-20AJ Datasheet - Page 260

• Manufacturer Part Number: ATMEGA88-20AJ
• Description: IC MCU AVR 8K 5V 20MHZ 32-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA88-20AJ

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATMEGA88-24AJ; ATMEGA88-24AJ

24.4
24.5
24.6
24.6.1
260
Software Break Points
Limitations of debugWIRE
Register Description
ATmega48/88/168
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 10 kΩ. 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
tion replaced by the BREAK instruction will be stored. When program execution is continued, 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 therefore
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.
The debugWIRE system shares system clock with the SPI module. Thus the PRSPI bit in the
PRR register must not be set when debugging. Setting the PRSPI bit will disable the clock to the
debugWIRE module and may lead to lockup of the device.
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 instruc-
R/W
5
0
CC
R/W
will not work.
4
0
DWDR[7:0]
R/W
3
0
R/W
2
0
R/W
1
0
R/W
0
0
2545S–AVR–07/10
DWDR