Quick description of avr-gdb.


Today avr-gdb works only as in circuit debugger because I don't have a
simulator. 
avr-gdb needed in monitor.

Monitor consists of two parts:
1) AVR part (0x1d0 bytes of code and 0x40 bytes of data);
2) PC part.

PC part of monitor can (with help of AVR part of monitor):
- read/write AVR registers (include SREG, PC and SP);
- read/write AVR memory;
- read/write AVR IO.
- put/clear up to 8 breakpoints;
- step one instruction.

AVR part of monitor written in C (avr-gcc).

AVR part of monitor stops only on source coded breakpoints (`TRAP()').
After stopping you can work with the AVR part (with chip).

PC and AVR connected as:
-------------------------------------------------------------
  Connect AVR with parallel port
        AVR                       Parallel Port
   Signal name   Pin             Pin  Signal name
   GND           20 ------------ 19   GND
   GND           20 ------------ 21   GND
   SCK            8 ------------  1   Strobe
   MOSI           6 ------------ 12   Out of paper
   MISO           7 ------------ 11   Busy
   Reset          9 ------------ 16   Init
   Connect parallel port pin 12 with parallel port pin 2 through diod
                                 Out of paper 12 ----|>|--- 2 Data 0
  This connection allow to use send_byte and program AVR flash 
  with Uros Platise `uisp' in `-dapa' mode.
----------------------------------------------------------------------

How the avr-gdb works:

The avr-gdb connects with monitor (PC part of monitor) through TCP
After connection: program in AVR runs until TRAP() executed.
(TRAP () is a source coded breakpoint). 
After a AVR program trap's you can :
- watch any global variables;
- disassemble functions;
- watch registers and local variables;
- up's and down's by stack;
- list source texts;
- run any function with parameters in AVR chip;
- any thing which GDB can;
- step one instruction;
- put breakpoints (up to 8);
- clear breakpoints;
- continue execution until next TRAP();
- stepping until TRAP () or any breakpoint;

continue AVR program only if no breakpoint sets (gdb command `c').
stepping AVR program if one or more breakpoint sets (gdb command `c').

Under emacs all this works as a native PC debugging except source
coded TRAP()'s.

You can use any gdb GUI frontend: xxgdb, Source Navigator, ...

-----------------------------------------------------------------------
			How to run

1. Compile a C program with `-g' command line option;
2. Write this program to AVR Flash. I'm use:
	avr-ld --oformat=srec a.out -o a.srec
	uisp -dapa --erase
	uisp -dapa --upload if=a.srec -v=3
3. Run AVR monitor. (`mon localhost' or `remon localhost');
4. Run avr-gdb;
5. Type following commands under avr-gdb:
	file a.out
	target avr localhost:11111
6. The program in AVR chip will be executed until the program
   reaches a source coded breakpoint ( TRAP(); ).