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SAVE

     Purpose:  Save memory to a device
Call address:  $FFD8 (hex)  65496 (decimal)
Communication registers:  A, X, Y
Preparatory routines:  SETLFS, SETNAM
Error returns:  5, 8, 9, READST
Stack requirements:  None
Registers affected:  A, X, Y

Description:

This routine saves a section of memory. Memory is saved from an indirect address on page 0 specified by the accumulator to the address stored in the X and Y registers. It is then sent to a logical file on an input/output device. The SETLFS and SETNAM routines must be used before calling this routine. However, a file name is not required to SAVE to device 1 (the DatassetteTM recorder). Any attempt to save to other devices without using a file name results in an error.

NOTE: Device 0 (the keyboard), device 2 (RS-232), and device 3 (the screen) cannot be SAVEd to. If the attempt is made, an error occurs, and the SAVE is stopped.

How to Use:

  1. Use the SETLFS routine and the SETNAM routine (unless a SAVE with no file name is desired on "a save to the tape recorder").
  2. Load two consecutive locations on page 0 with a pointer to the start of your save (in standard 6502 low byte first, high byte next format).
  3. Load the accumulator with the single byte page zero offset to the pointer.
  4. Load the X and Y registers with the low byte and high byte respectively of the location of the end of the save.
  5. Call this routine.

EXAMPLE:

     LDA #1              ;DEVICE=1:CASSETTE
     JSR SETLFS
     LDA #0              ;NO FILE NAME
     JSR SETNAM
     LDA PROG            ;LOAD START ADDRESS OF SAVE
     STA TXTTAB          ;(LOW BYTE)
     LDA PROG+1
     STA TXTTAB+1        ;(HIGH BYTE)
     LDX VARTAB          ;LOAD X WITH LOW BYTE OF END OF SAVE
     LDY VARTAB+1        ;LOAD Y WITH HIGH BYTE
     LDA #<TXTTAB        ;LOAD ACCUMULATOR WITH PAGE 0 OFFSET
     JSR SAVE
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