Purpose: Set bottom of memory
Call address: $FF9C (hex) 65436 (decimal)
Communication registers:X, Y
Preparatory routines: None
Error returns: None
Stack requirements: None
Registers affected: X, Y
Description: This routine is used to set the bottom of the memory. If the accumulator carry bit is set when this routine is called, a pointer to the lowest byte of RAM is returned in the X and Y registers. On the unexpanded Commodore 64 the initial value of this pointer is $0800 (2048 in decimal). If the accumulator carry bit is clear (-O) when this routine is called, the values of the X and Y registers are transferred to the low and high bytes, respectively, of the pointer to the beginning of RAM.
How to Use:
TO READ THE BOTTOM OF RAM
EXAMPLE:
;MOVE BOTTOM OF MEMORY UP 1 PAGE SEC ;READ MEMORY BOTTOM JSR MEMBOT INY CLC ;SET MEMORY BOTTOM TO NEW VALUE JSR MEMBOT
This page has been created by Sami Rautiainen. | |
Read the small print. | Last updated December 16, 2002. |