Lookup table on a hex 100 boundary

dg4mec · Joined: 12 Jan 2005 Posts: 3 Location: 90439 Nürnberg

I look for a way to place a lookup table on a hex 100 boundary at end of flash ram. Is in Bascom-AVR a compiler function like in assembler " .org address "

DToolan · Posted: Wed Jan 12, 2005 8:35 pm Post subject:

You can force the locations for variables in the following manner...

DIM MyArray1(36) As BYTE at $100 '<- RAM declaration
DIM MyArray2(36) As ERAM BYTE at $100 '<- EEPROM declaration

dg4mec · Joined: 12 Jan 2005 Posts: 3 Location: 90439 Nürnberg

Many thanks to DToolan for his replay.

When I posted my question I gave to les info about my problem.
The table I use is 1024 Bytes long, so it will not fit in EERAM (512 Bytes) or it will consume all SRAM (1024 Bytes), based on a ATMega162 chip. For this reason I have to place it in "FLASH RAM".

Thanks for Your support.

DToolan · Posted: Thu Jan 13, 2005 9:17 pm Post subject:

By "flash ram", I guess you mean the program storage area. You can use a DATA statement for your lookup table and that would place your table at the end of the used program storage. This would not necessarilly be at a hex 100 boundry though. A comma at the end of a line will continue the DATA statement through subsequent lines. Leave the comma off the last line of your DATA statement. The first element of a DATA statement is element zero.

Pretending a two dimensional lookup table that is 32 x 32 (1024 elements)... row 1, column 21 would be the 20th element. Also, since a byte can only go to 255, you may have to chop up your table into 32 rows. You'll have to experiment with the DATA statement and using bytes, words, etc. for pointers. The Bascom DATA statement can sometimes be finicky and while it may compile without error, you might not get the data element you expect. For instance, stick with one data type in your DATA statement (ASCII, Hex, Binary... whatever you choose). Mixing data types in the data statement... DATA "A", 65, &H41 may not always produce equal results even though all three of those items are equal.

It's possible you may be able to get by with one large table of 1024 and use a word for POSITION (I haven't done one larger than 255). There are many ways to accomplish any one task.

dg4mec · Joined: 12 Jan 2005 Posts: 3 Location: 90439 Nürnberg

I used already the DATA statement to store my table in program area. The table was correctly stored, but in the middle of the machine code, and not on a hex &H100 boundary. Since the table is accessed by an fast assembler loop with only 6 instructions, I need the hex &H100 boundary. The table it self consists of 4 parts each 256 bytes long (sine, triangle, saw tooth and a square wave table).

I solved my problem using the compiler directive " $BOOT " which moved the DATA area to top of Program storage. The address I had to enter is the address divided by 2 (word address), but this is not documented in the help function.

Thanks to all which investigated on my problem.