Loader.PDF

ATm8LD 1 AT Mega8 128Words Boot Loader

The Boot loader is only 128 words of code. It require one pin to tell when to boot.

In this case PinC.1 is used. The aumont of memory needed for loader is only 256

bytes . The Code for boot loader is modification of program written by David

Moran - BootM8.Bas. I chose this code because of the small size and simplicity.

In my edition of the loader boot process starts when PinC.1 is short to GND.

Other wise processor starts the main code without any wait.

The speed of sending data to CPU is setup for 19,200 bps what is optimum to

Use with internal 4 or 8 Mhz oscillator.

The fusebits need to be set for 128 bytes for the boot code,

starting at $F80

Fusebits: Boot Application Bootloader End of Boot Reset

BOOTSZ1 BOOTSZ0 Size Flash Section Flash Section Application Address

1 1 128 $000 - $F7F $F80 - $FFF $F7F $F80

Standard Intel hex file can be sent: (spaces added for readability)

All record sizes must be even, AVR uses WORDs, not bytes

:Size Address Type Data Bytes Checksum

:10 00 00 00 26 C0 B3 C0 B3 C0 B3 C0 B3 C0 C5 C0 C5 C0 D0 C0 A4

:10 00 10 00 DB C0 E4 C0 ED C0 30 31 32 33 34 35 36 37 38 39 E7

:10 05 30 00 55 DF 08 95 57 E5 57 DF 52 E5 55 DF 54 E5 53 DF A2

:10 05 40 00 5C E2 51 DF 53 2F 52 95 49 DF 53 2F 47 DF 01 D0 33

:0B 05 50 00 08 95 5D E0 48 DF 5A E0 46 DF 08 95 A2 DC

:00 00 00 01 FF

Program for sending data to CPU is written in Visual Basic V6.0

ATm8LD 2 AT Mega8 128Words Boot Loader

ATm8Ld require to select com port . The message box will prompt you to set the

port number on first run. If you want to change port any way change the number

In text box , than hit CHANGE, Program will finish rewriting registry with new

port number. After next start up program is ready to operate on the port.

The Intel hex code of the program must be preloaded by using LOAD

Program use widows file picker and full path will be remember in registry also

The internal buffer will be fill with file . After next start up the same file will be

used until you load other.

ATm8LD 3 AT Mega8 128Words Boot Loader

After Loading the file, set the switch in boot position.

Power off ,and power on the board .Program will respond with

Labels B ? instead of labels @ @

ATm8LD 4 AT Mega8 128Words Boot Loader

Now hit the SEND to send hex file to board.

ATm8LD 5 AT Mega8 128Words Boot Loader

Board will receive record by record hex code of micro program.

Each record starts with labels B ? . I case of error the labels can change

B ! for header mismatch and B C for bad check sum.

Each record will be program into flash memory. The loader is only

For flash code.