Rainbow Electronics ATtiny2313 - Manual (Page 153)

153
ATtiny2313
2543A–AVR–08/03
debugWIRE On-chip
Debug System
Features • Complete Program Flow Control
• Emulates All On-chip Functions, Both Digital and Analog , except RESET Pin
• Real-time Operation
• Symbolic Debugging Support (Both at C and Assembler Source Level, or for Other HLLs)
• Unlimited Number of Program Break Points (Using Software Break Points)
• Non-intrusive Operation
• Electrical Characteristics Identical to Real Device
• Automatic Configuration System
• High-Speed Operation
• Programming of Non-volatile Memories
Overview The debugWIRE On-chip debug system uses a One-wire, bi-directional interface to con-
trol the program flow, execute AVR instructions in the CPU and to program the different
non-volatile memories.
Physical Interface When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are unpro-
grammed, the debugWIRE system within the target device is activated. The RESET port
pin is configured as a wire-AND (open-drain) bi-directional I/O pin with pull-up enabled
and becomes the communication gateway between target and emulator.
Figure 66. The debugWIRE Setup
Figure 66 shows the schematic of a target MCU, with debugWIRE enabled, and the
emulator connector. The system clock is not affected by debugWIRE and will always be
the clock source selected by the CKSEL Fuses.
When designing a system where debugWIRE will be used, the following observations
must be made for correct operation:
• Pull-Up resistor on the dW/(RESET) line must be larger than 10k. However, the pull-
up resistor is optional.
• Connecting the RESET pin directly to V
CC
will not work.
dW
GND
dW(RESET)
VCC
1.8 - 5.5V