RTX51 TINY: SAVING AND RESTORING XDATA BANKING INFORMATION
Information in this article applies to:
I am using the Keil PK51, RTX51 Tiny Version 2, and far memory to access 4 banks of SRAM. The XDATA Banking is configured in the XBANKING.A51 file. I need to save and restore the XDATA banking information when RTX51 Tiny performs a task switch.
I'm using code banking (configured via L51_BANK.A51) and that works just fine with RTX51 Tiny. The XDATA Banking information should be just as easily saved. Can you point me in the right direction so that I can modify CONF_TNY.A51 myself?
Yes. It is easy to add code to save and restore the XDATA banking details. You must modify the CONF_TNY.A51 and OS_CREATE.A51 files.
You should add the XDATA banking save/restore code at the same location where the CODE_BANKING support is introduced via the IF (CODE_BANKING <> 0) directives.
There are 2 occurrances of the code sequence that saves the bank information in CONF_TNY.A51. You should add the XDATA banking save/restore code to both. For example:
IF (CODE_BANKING <> 0) PUSH ?B_CURRENTBANK ENDIF ; *** Add code here to save the ; *** XDATA banking port value to the stack
The code to restore the XDATA banking port must be inserted in the following code sequence:
NoEvent: CLR ACC.B_RUN ; Clear RUN bit XCH A,@R0 SETB EA ANL A,#K_RUN ORL AR7,A ; *** Add code here to restore the ; *** XDATA banking port value from the stack IF (TIMESHARING <> 0) IF (CODE_BANKING) POP ACC CALL ?B_RESTORE_BANK ENDIF CLR ?RTX_TS_DELAY RET
You must modify the OS_CREATE.A51 source file to adjust the stack layout. There are several places where the stack is adjusted as shown below:
$IF (CODE_BANKING) DEC R1 ; *** Add a DEC R1 for each byte ; *** you save on the stack $ENDIF and $IF (CODE_BANKING) INC @R0 ; *** Add an INC R1 for each byte ; *** you save on the stack $ENDIF
You must add code to the following to select the default XDATA bank that is selected when the task starts.
$IF (CODE_BANKING) EXTRN DATA (?B_CURRENTBANK) INC R0 MOV A,?B_CURRENTBANK ; Set the initial code bank MOV @R0,A ; *** Add code for each byte restored ; *** that selects the XDATA banking port ; INC R0 ; MOV A,#0 ; default XDATA banking port ; MOV @R0,A
Last Reviewed: Tuesday, November 5, 2002
of your data.