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How to READ from the data table with offset?

 
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mrak

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Joined: 14 Dec 2005
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PostPosted: Fri Oct 17, 2014 7:44 am    Post subject: How to READ from the data table with offset? Reply with quote

The READ command is convenient for sequential reading of data from the data table but the RESTORE command always sets the data pointer at the beginning of the table.


Could you, please, advise how to skip over a block of data in the table and start sequential reading from the offset point (i.e. Nth element of the table)?


Thanks,
makarak

(BASCOM-AVR version : 2.0.7.7 )
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MWS

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Joined: 22 Aug 2009
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PostPosted: Fri Oct 17, 2014 8:59 am    Post subject: Reply with quote

Processor registers R8/R9 hold the pointer used by Read(), it's possible to add an offset there.
Care has to be taken with processors of > 64k flash, where RAMPZ needs to be taken care of.
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O-Family

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Joined: 23 May 2010
Posts: 237
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PostPosted: Sat Oct 18, 2014 1:43 am    Post subject: Reply with quote

Hi

"Lookup" if the numeric data.
"Lookupstr" if the string data.

In changing to this instruction, do you have any problems?
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mrak

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Joined: 14 Dec 2005
Posts: 24

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PostPosted: Mon Nov 03, 2014 8:43 pm    Post subject: Reply with quote

O-Family wrote:
Hi

"Lookup" if the numeric data.
"Lookupstr" if the string data.

In changing to this instruction, do you have any problems?


O-Family,

I'm aware of the both commands.
I need to jump over to the offset point and next do the sequential read. Therefore the lookup commands are not very convenient enough here as require explicite calculation of the current pointer position. Referring to a pair of the R8/R9 registers approach suggested by Mark works fine and fully meet my expectation.
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mrak

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Joined: 14 Dec 2005
Posts: 24

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PostPosted: Mon Nov 03, 2014 8:46 pm    Post subject: Reply with quote

O-Family wrote:
Hi

"Lookup" if the numeric data.
"Lookupstr" if the string data.

In changing to this instruction, do you have any problems?


O-Family,

I'm aware of the both commands.
I need to jump over to the offset point and next do the sequential read. Therefore the lookup commands are not very convenient enough here as require explicite calculation of the current pointer position. Referring to a pair of the R8/R9 registers approach suggested by Mark works fine and fully meet my expectation.
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O-Family

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Joined: 23 May 2010
Posts: 237
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PostPosted: Tue Nov 04, 2014 1:06 pm    Post subject: Reply with quote

If you can write using an assembler, operation of a data table can also choose various kinds of methods.

I proposed the method of operating a table on BASIC grammar.
If the same is the type of number that is prepared for data statement, "Lookup" instruction by varying the index, and operation equivalent to a sequential lead is possible.
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EDC

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Joined: 26 Mar 2014
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PostPosted: Tue Nov 04, 2014 3:26 pm    Post subject: Reply with quote

See my answear in SUB topic and test this in simulator to understand that offset can be calculated even on strings table Smile
Example show "Poland" in first Line and "Bartek" in the second because strings are readed to its end.
Code:
$sim
$regfile = "m8def.dat"
$crystal = 16000000
$hwstack = 64
$swstack = 64
$framesize = 64

Dim Address As Word
Dim N As Byte
Dim Items(5) As Byte
Dim Offset As Word

Offset = 2                                                  'TRY OTHER VALUES

Declare Sub Show_array(byval Address As Word , Byval Linia As Byte , Byval Offset As Word)

Cls

Address = Loadlabel(label_1 )
Call Show_array(address , 1 , 6)
Call Show_array(address , 2 , 13)
Macro Restore_address
   Loadadr Address , X                                      'restore address
   !LD    R8,X+
   !LD    R9,X
End Macro

'** pro forma
Do
nop
Loop
End
'** End **

Sub Show_array(byval Address As Word , Byval Linia As Byte, Byval Offset As Word)
     Local Addr_to As Word
     Local Text As String * 20

  Locate Linia , 1

  Address = Address + Offset

     Restore_address                                        'macro is used


     Read Text
     Lcd Text


End Sub


Label_1:
Data "Hello Poland" , "Bartek"
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O-Family

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Joined: 23 May 2010
Posts: 237
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PostPosted: Tue Nov 04, 2014 4:21 pm    Post subject: Reply with quote

It is a method peculiar to BASCOM to operate the registers R8 and R9 directly.
I would like to think more simply.

Code:
$sim
$regfile = "m8def.dat"
$crystal = 16000000
$hwstack = 64
$swstack = 64
$framesize = 64
$baud = 9600

   Dim Offset As Word , Temp1 As Byte , Temp2 As Byte

   Offset = 16                                              'ASCII "0" Font character.
   Offset = Offset * 8                                      '8 bytes step.
   Offset = Offset + 4                                      'Font information is skipped.

   For Temp1 = 1 To 8                                       'Get 8 bytes.
      Temp2 = Lookup(offset , Font8x8)
      Print Temp2
      Offset = Offset + 1
   Next Temp1

   End

$include "font8x8.font"                                     '"lcdgraph" Font data.
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albertsm

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Joined: 09 Apr 2004
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PostPosted: Tue Nov 04, 2014 10:07 pm    Post subject: Reply with quote

maybe good to know that in 2078 the label parameter can be a numeric value too. This allows to pass to a sub/function.
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Mark
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O-Family

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Joined: 23 May 2010
Posts: 237
Location: Japan

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PostPosted: Wed Nov 05, 2014 1:31 am    Post subject: Reply with quote

Hi Mark

Yes, in 2078(2077 SLA), the address of the label was passed by the variable.
The following is possible.
It is very good!

Code:
$sim
$regfile = "m8def.dat"
$crystal = 16000000
$hwstack = 64
$swstack = 64
$framesize = 64
$baud = 9600

   Dim Offset As Word , Temp1 As Byte , Temp2 As Byte , ___fonttable As Word


   Setfont Font8x8                                          '*** Standard font of BASCOM ***
   '
   Offset = 16                                              'ASCII "0" Font character.
   Offset = Offset * 8                                      '8 bytes step.
   Offset = Offset + 4                                      'Font information is skipped.
   For Temp1 = 1 To 8                                       'Get 8 bytes.
      Temp2 = Lookup(offset , ___fonttable)
      Print Temp2
      Offset = Offset + 1
   Next Temp1


   Setfont Font8x8_user                                     '*** Font made by the user ***
   '
   Offset = 16                                              'ASCII "0" Font character.
   Offset = Offset * 8                                      '8 bytes step.
   Offset = Offset + 4                                      'Font information is skipped.
   For Temp1 = 1 To 8                                       'Get 8 bytes.
      Temp2 = Lookup(offset , ___fonttable)
      Print Temp2
      Offset = Offset + 1
   Next Temp1

   End


$include "font8x8.font"                                     '"lcdgraph" Font data.

$include "font8x8_User.font"                                'User Font data.
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MWS

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Joined: 22 Aug 2009
Posts: 1915

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PostPosted: Wed Nov 05, 2014 12:48 pm    Post subject: Reply with quote

albertsm wrote:
maybe good to know that in 2078 the label parameter can be a numeric value too. This allows to pass to a sub/function.


How is RAMPZ taken care of in this variable, if flash > 64k?

May I suggest an additional parameter for the Lookup()-function, which sets the pointer for sequential Read's immediately on the byte following the lookup?
This way the first value can be retrieved by an absolute read and the following by sequential reads.
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O-Family

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Posts: 237
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PostPosted: Wed Nov 05, 2014 2:03 pm    Post subject: Reply with quote

MWS wrote:
How is RAMPZ taken care of in this variable, if flash > 64k?

I think that it is managed by the LONG variable.
See an assembler output!

Code:
[ATmega8]
0034 : 2466                CLR   R6
0035 : EBE2                LDI   ZL,LOW(S01B2)
0036 : E0F1                LDI   ZH,HIGH(S01B2)
0037 : E6A4                LDI   XL,LOW(S0064)
0038 : E0B0                LDI   XH,HIGH(S0064)
0039 : 93ED                ST    X+,ZL
003A : 93FC                ST    X,ZH


[ATmega1284P]
006C : 2466                CLR   R6
006D : E5E6                LDI   ZL,LOW(S0256)
006E : E0F2                LDI   ZH,HIGH(S0256)
006F : 940E 07A8           CALL  L07A8
0071 : E0A5                LDI   XL,LOW(S0105)
0072 : E0B1                LDI   XH,HIGH(S0105)
0073 : 93ED                ST    X+,ZL
0074 : 93FD                ST    X+,ZH
0075 : B78B                IN    R24,$3B  [RAMPZ]
0076 : 938C                ST    X,R24

07A2 : 930F                PUSH  R16
07A3 : E001                LDI   R16,$01
07A4 : BF0B        L07A4:  OUT   $3B,R16
07A5 : 910F                POP   R16
07A6 : 9488                CLC
07A7 : 9508                RET

07A8 : 930F        L07A8:  PUSH  R16
07A9 : 2700                CLR   R16
07AA : CFF9                RJMP  L07A4
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MWS

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Joined: 22 Aug 2009
Posts: 1915

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PostPosted: Wed Nov 05, 2014 6:01 pm    Post subject: Reply with quote

O-Family wrote:
I think that it is managed by the LONG variable.
See an assembler output!

[code]
[ATmega1284P]
006C : 2466 CLR R6
006D : E5E6 LDI ZL,LOW(S0256)
006E : E0F2 LDI ZH,HIGH(S0256)
006F : 940E 07A8 CALL L07A8
0071 : E0A5 LDI XL,LOW(S0105)
0072 : E0B1 LDI XH,HIGH(S0105)
0073 : 93ED ST X+,ZL
0074 : 93FD ST X+,ZH
0075 : B78B IN R24,$3B [RAMPZ]
0076 : 938C ST X,R24

07A2 : 930F PUSH R16
07A3 : E001 LDI R16,$01
07A4 : BF0B L07A4: OUT $3B,R16
07A5 : 910F POP R16
07A6 : 9488 CLC
07A7 : 9508 RET

07A8 : 930F L07A8: PUSH R16
07A9 : 2700 CLR R16
07AA : CFF9 RJMP L07A4

If you think that, you think wrong.
Look for the line, where the codepage is set, then you see it is hard-coded to page 0.

The compiler knows addresses of all labels, so it knows the codepage of the label-start.
But if the label-start is just below a 64k boundary, and the target address is on the next page, knowing only the label-start is not enough.
The true page and address within page has to be calculated from the pointer-variable, and it has to be done dynamically. The variable must thus contain all information to the target, means the absolute position within flash.
Bascom can use a subroutine then, to calculate the page and position within page.

The shown code does not do this, it reads only the word position within a page and assumes a fixed page.
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O-Family

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Joined: 23 May 2010
Posts: 237
Location: Japan

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PostPosted: Thu Nov 06, 2014 1:01 am    Post subject: Reply with quote

This assembler code is the thing which compiled and disassembled the above-mentioned Font extraction program.
The shown portion is the code which extracted the portion which stores the address of a label in a variable.

When the Flash of a chip are 64K or more, it is saying that it is automatically stored in a LONG variable.
Therefore, a user also has to prepare a LONG variable.
Moreover, by the "Lookup" processing routine, if 64K is exceeded, it is programmed to change RAMPZ.
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