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far types

David Pleydell

I've tried to mod the xbanking link file to generate paging for my device.

I was trying to use segment B which is defined between 8000-BFFF. Then page into this to give 128k.

I have set the HData to 0000-1FFFF in the options for far data.

Here are the mods i made.

LOAD_BANK MACRO
LOCAL lab
MOV DPL,R1
MOV DPH,R2
ORL DPH,#80H
;Now generate the page
MOV A,R2
RL A
RL A
ANL A,#03H
MOV ?C?XPAGE1SFR,A

Then used one of the examples from banking and tried this.

FVAR (char, 0x15678) = 0x5A;
i = FVAR (char, 0x15678);

i comes out to be 1. Stepping through the assembly code looks fine.

Is this correct usage?

David

  • 0

    This example is from the far memory section and the simulator reports an error when performing this code.
    FVAR (char, 0x015678) = 0x5A;
    i = FVAR (char, 0x015678);

    Also using unsigned char far large_array[0xC000]; still places the array in the xdata segment.

    When stepping through the simulator R3 contains 01 instead of 02 for far data.

    David

  • 0 in reply to David Pleydell

    Make sure that you selected the LX51 linker and AX51 assembler when you select the device from the device database.

    Jon

  • 0

    I have set the HData to 0000-1FFFF in the options for far data.

    Oops. I missed this in the original post.

    Take a look at this table from XBANKING.A51:

    ; Each function gets as a parameter the memory address with 3 BYTE POINTER    *
; representation in the CPU registers R1/R2/R3.  The register R3 holds the    *
; memory type.  The C51 compiler uses the following memory types:             *
;                                                                             *
; R3 Value | Memory Type | Memory Class | Address Range                       *
; -----------------------+--------------+--------------------------           *
;    00    | data/idata  | DATA/IDATA   | I:0x00     .. I:0xFF                *
;    01    | xdata       | XDATA        | X:0x0000   .. X:0xFFFF              *
;  02..7F  | far         | HDATA        | X:0x010000 .. X:0x7E0000            *
;  80..FD  | far const   | HCONST       | C:0x800000 .. C:0xFD0000 (see note) *
;    FE    | pdata       | XDATA        | one 256-byte page in XDATA memory   *
;    FF    | code        | CODE         | C:0x0000   .. C:0xFFFF              *

    From this, I think you need to set your HDATA range from 0x020000-0x03FFFF.

    If you access anything from 0x000000-0x00FFFF, the compiler assumes this is in IDATA and never calls the XBANKING routines.

    Anything in the range 0x010000-0x01FFFF is in XDATA. Accesses to this range also do not call the XBANKING routines.

    Jon

  • 0 in reply to Jon Ward

    The far types are between 02.7F so if i define the data to be of type far wouldn't it then call these routines and pass this in via R3?

    Just because the ram is xdata does that matter?

    Also the example project, ADuC812 which is supposed to show the usage of far types actually doesn't work. The simulator generates an access violation on the far memory calls. HData is set to the ranges you talk about it.
    I haven't change this example but was hoping to use it as a guide.

    David