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VECTOR

     Purpose:  Manage RAM vectors
Call address:  $FF8D (hex)  65421 (decimal)
Communication registers:  X, Y
Preparatory routines:  None
Error returns:  None
Stack requirements:  2
Registers affected:  A, X, Y

Description:

This routine manages all system vector jump addresses stored in RAM. Calling this routine with the the accumulator carry bit set stores the current contents of the RAM vectors in a list pointed to by the X and Y registers. When this routine is called with the carry clear, the user list pointed to by the X and Y registers is transferred to the system RAM vectors. The RAM vectors are listed in the memory map.

SYSTEM RAM VECTORS LISTING

RETURNED LOCATION [LOW BYTE] VECTOR [HIGH BYTE]
X + 256 * Y + 0 CINV + 1
+ 2 CBINV + 3
+ 4 NMINV + 5
+ 6 IOPEN + 7
+ 8 ICLOSE + 9
+10 ICHKIN + 11
+ 12 ICKOUT + 13
+ 14 ICLRCH + 15
+ 16 IBASIN + 17
+ 18 IBSOUT + 19
+ 20 ISTOP + 21
+ 22 IGETIN + 23
+ 24 ICLALL + 25
+ 26 USRCMD + 27
+ 28 ILOAD + 29
+ 30 ISAVE + 31
TOTAL BYTES: 32

NOTE: This routine requires caution in its use. The best way to use it is to first read the entire vector contents into the user area, alter the desired vectors, and then copy the contents back to the system vectors.

How to Use:

READ THE SYSTEM RAM VECTORS

  1. Set the carry.
  2. Set the X and y registers to the address to put the vectors.
  3. Call this routine.

LOAD THE SYSTEM RAM VECTORS

  1. Clear the carry bit.
  2. Set the X and Y registers to the address of the vector list in RAM that must be loaded.
  3. Call this routine.

EXAMPLE:

     ;CHANGE THE INPUT ROUTINES TO NEW SYSTEM
     LDX #<USER
     LDY #>USER
     SEC
     JSR VECTOR      ;READ OLD VECTORS
     LDA #<MYINP     ;CHANGE CHKIN VECTOR
     STA USER+10
     LDA #>MYINP
     STA USER+11
     LDX #<USER
     LDY #>USER
     CLC
     JSR VECTOR      ;ALTER SYSTEM
     ...
USER *=*+32
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