How to create a 21 bit address and separate into three bytes for Atmel serial eeprom?

[BrianS]

I am using a atmel AT45DB161D serial eeprom and need to do a continious memory read.
I am programming a pic 18f4620.

This is the code the format of the 21 bits I need to send.
I would need to send this as 3 bytes but don't know how to do this correctly.

/      /<---------Page Addr--------------->/<------starting byte----->/ 
/X,X,X,20,19,18,17,16/15,14,13,12,11,10,09,08/07,06,05,04,03,02,01,00/

The XXX are don't care bits.

In another compiler I can do this by using a Dword (32 bits) variable and the split the 32 bits into 4 bytes. Using only the last 3 bytes. This is accomplished using a pascal compiler using following code example.

procedure mm_rd_cmd(start:dword);
begin
  BusyWait;
  CS_Low;
  SPI1_Write($E8);
  SPI1_Write(higher(start));
  SPI1_Write(hi(start));
  SPI1_Write(lo(start));
  SPI1_Write($00);
  SPI1_Write($00);
  SPI1_Write($00);
  SPI1_Write($00);
end;

The higher, hi, and lo break the 24 bits of var "start" (a 32 bit Dword) into 3 lower bytes. Discarding the highest byte (bits 25 - 32).
Is there a way to get Picbasic Pro to do a similar thing. Help is greatly appreciated.

Thanks,
Bryan

[HenrikOlsson]

Hi,
What version of PBP do you have? As of v2.50 32bit variables are available in PBP...

myLong VAR LONG

And you can access the individual BYTES in a LONG with myLong.BYTE0, myLong.BYTE1 and so on.

/Henrik.

[BrianS]

Hi,
What version of PBP do you have? As of v2.50 32bit variables are available in PBP...

myLong VAR LONG

And you can access the individual BYTES in a LONG with myLong.BYTE0, myLong.BYTE1 and so on.

/Henrik.

Looks like a good solution. I tried it but it give an incorrect result on the third highest byte.
here a portion of the code.

rd_addr2 var long

rd_addr2 = $01FE   

Readout_Strings:
gosub BusyWait
Low CSEE
Shiftout SDO,SCK,Msbfirst,[$E8]
Shiftout SDO,SCK,Msbfirst,[rd_addr2.byte2]
Shiftout SDO,SCK,Msbfirst,[rd_addr2.byte1]
Shiftout SDO,SCK,Msbfirst,[rd_addr2.byte0]
Shiftout SDO,SCK,Msbfirst,[$00]
Shiftout SDO,SCK,Msbfirst,[$00]
Shiftout SDO,SCK,Msbfirst,[$00]
Shiftout SDO,SCK,Msbfirst,[$00]
return

rd_addr2.byte2 = 16 or binary 10000 which is wrong it should be 0. Nothing else changes the value of rd_addr2 it's value is defined at the start of the code and nothing else alters it. Is, there any possible explaination for this that can cause the value to be wrong?

Thanks,
Bryan

[HenrikOlsson]

Hi,
I just tried the following code here:

rd_addr2 VAR LONG
rd_addr2 = $01FE
Pause 1000
HSEROUT [DEC3 rd_addr2.BYTE3, ",", DEC3 rd_addr2.BYTE2, ",", DEC3 rd_addr2.BYTE1, ",", DEC3 rd_addr2.BYTE0,10,13]

And it displays 000,000,001,254 on the serial terminal (see attached screenshot) so IT seems to work. Don't know why you would get 16.....

/Henrik.

[BryanSw]

Hi,
I just tried the following code here:

rd_addr2 VAR LONG
rd_addr2 = $01FE
Pause 1000
HSEROUT [DEC3 rd_addr2.BYTE3, ",", DEC3 rd_addr2.BYTE2, ",", DEC3 rd_addr2.BYTE1, ",", DEC3 rd_addr2.BYTE0,10,13]

And it displays 000,000,001,254 on the serial terminal (see attached screenshot) so IT seems to work. Don't know why you would get 16.....

/Henrik.

Really got me. I'll try the code all by itself without anything else and see what I get. Won't have a reply till tomorrow about this because I'm not at work now to try it. Hope it is something I can correct. Really need to get this working for a project at work. I use other compilers at home for personal use by at work I have to use PBP.

Thanks,
Bryan

[BryanSw]

OK, I got it working normally. What I had to do to make it work makes no sense to me because it should have worked the way I had it. Anyway I had to move

rd_addr2 VAR LONG
rd_addr2 = $01FE

into the same sub routine as

Pause 1000
HSEROUT [DEC3 rd_addr2.BYTE3, ",", DEC3 rd_addr2.BYTE2, ",", DEC3 rd_addr2.BYTE1, ",", DEC3 rd_addr2.BYTE0,10,13]

Then it worked.
If I put the
rd_addr2 VAR LONG
rd_addr2 = $01FE
at the top of my program with my global vars definations and assign a value to
rd_addr2 also at the top of my program it would give me an incorrect result.

I will play around with this some more as there has to be a reason for it. I am not assigning anything else at any othe time to rd_addr2.

Thanks,
Bryan