read write program memory

[cluster]

hello,

can any one tell me how to write and read program memory?
i am working on 18f46j50. i need to store some data coming from usart so instead of using external eeprom i wanted it to write into program memory

thank you

[octal]

check http://www.sfcompiler.co.uk/wiki/pmwiki ... .ROMBuffer

[cluster]

check http://www.sfcompiler.co.uk/wiki/pmwiki ... .ROMBuffer

thanks for the link octal. but how do i write to address? like if i wanted to write 0 to address from $1000-$1400 then how to do that?
i saw in ROM module there is a variable "FROMAddress", i tried accessing it ROM.FROMAddress = $1000 but compiler returned error.

[octal]

if you need so much granularity, check also
http://www.sfcompiler.co.uk/wiki/pmwiki ... moryAccess

[cluster]

if you need so much granularity, check also
http://www.sfcompiler.co.uk/wiki/pmwiki ... moryAccess

Hi octal,
thank you for the help, but still i am unable to get it working...
as example given in the link i made a simple program as below, its not working properly. I am trying to write 64 bytes as mentioned in datasheet but for some reason its writing 128 byte. can you please take a look at the code and memory dump, i would really appreciate it.

thank you

Code: Select all

Program RWT

Device = 18F46J50
Clock = 48
Config OSC = HSPLL
Config PLLDIV = 5 'PLL division

#option USB_SERVICE = False 

#option ROM_BLOCK_SIZE = 64

Include "usbhid.bas"
Include "string.bas"
include "MemoryAccess.BAS"

Dim Address As Word
Dim index As byte

Structure TTXReport
   Message As String
End Structure

Structure TRXReport
   Message As String
End Structure 

Dim TXReport As TTXReport Absolute TXReportRAM 
Dim RXReport As TRXReport Absolute RXReportRAM
Dim Service As PORTA.0


Clear(HID.Buffer)
High(Service)

While true
    
    HID.Service
    If HID.Attached Then
        Low(Service)
        If DataAvailable Then
            ReadReport
                Select RXReport.Message
                    Case "0"
                        Address = $800
                        EraseBlock(Address)
                        For index = 0 To 63 
                            WriteAt(Address,index) 
                            Inc (Address) 
                        Next 
                        CloseWrite
                        TXReport.Message = "Written"                                                
                    Case "1"
                        TXReport.Message = "Resetting Device..."
                        UCON = 0                             
                        UIE = 0                                 
                        UCON.3 = 0
                        DelayMS(100)
                        ASM
                            RESET
                        End ASM
                    Else
                        TXReport.Message = RXReport.Message
                EndSelect
            WriteReport
        EndIf
    Else
        High(Service)
    EndIf
   
Wend
 
End Program 

memory dump, left most column are address

Code: Select all

07F0	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	 FFFF
0800	0100	0302	0504	0706	0908	0B0A	0D0C    0F0E
0810	1110	1312	1514	1716	1918	1B1A	1D1C    1F1E
0820	2120	2322	2524	2726	2928	2B2A	2D2C    2F2E
0830	3130	3332	3534	3736	3938	3B3A	3D3C    F13E
0840	0100	0302	0504	0706	0908	0B0A	0D0C    0F0E
0850	1110	1312	1514	1716	1918	1B1A	1D1C    1F1E
0860	2120	2322	2524	2726	2928	2B2A	2D2C    2F2E
0870	3130	3332	3534	3736	3938	3B3A	3D3C    3F3E
0880	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	 FFFF

[cluster]

ok got it working for the 64byte block, just commented out CloseWrite
but still its not writing for the last 64th byte, it always write F1 there
what i am doing wrong... i have also tried changing index 0 to 64 still its not writing 64th byte..

Code: Select all

07F0	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF
0800	0000	0000	0000	0000	0000	0000	0000	0000
0810	0000	0000	0000	0000	0000	0000	0000	0000
0820	0000	0000	0000	0000	0000	0000	0000	0000
0830	0000	0000	0000	0000	0000	0000	0000	F100 <-----
0840	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF	FFFF

[Jerry Messina]

I don't think you're doing anything wrong. The code in MemoryAccess.bas doesn't look correct. It seems that WriteItem() is going to call CloseWrite() one byte too early, and that matches what you're seeing.

WriteItem() uses the following to actually write a byte. It uses the asm table write instruction that automatically increments the TABLEPTR register after it writes.

Code: Select all

// table write
    Inline Sub TableWrite()
      ASM
      TBLWT*+
      End ASM
    End Sub

But, WriteItem also increments the TABLEPTR register

Code: Select all

{
****************************************************************************
* Name    : WriteItem                                                      *
* Purpose : Write a byte to program memory                                 *
****************************************************************************
}
    Public Sub WriteItem (pValue As TABLAT)
      TableWrite       
      If (WriteBlockSize And Byte(TBLPTRL+1)) = 0 Then
         CloseWrite
      EndIf
      Inc(TABLEPTR)
    End Sub

If the ROM_BLOCK_SIZE=64, then the constant WriteBlockSize=63, and CloseWrite() will be called when WriteItem() is called with TABLEPTR = 62.

Try changing TableWrite() to this and see if it works better

Code: Select all

// table write
    Inline Sub TableWrite()
      ASM
      TBLWT*
      End ASM
    End Sub

[cluster]

thank you very much Jerry and Octal its working now...

[Mikeclx]

Thanks Jerry,
That little + cost me hours of time to work around last year and now i understand why it was all not working correctly...

Regards,

Mike

[Jason]

Love this post... I tried to get program memory access working a while ago and never quite did. I think it's time to dive back in there and own it.