Function Name: MEMBOT

Purpose: Set/read bottom of system RAM
Call address: $FF9C (hex) 65436 (decimal)
Preparation:

	Registers:	.X = lsb of MEMSTR
			.Y = msb of MEMSTR
	Memory:		system map
	Flags:		.C = 0 -> set bot of memory
			.C = 1 -> read bot of memory
	Calls:		none

	Registers:	.X = lsb of MEMSTR
			.Y = msb of MEMstr
	Memory:		MEMSTR ($A05)
	Flags:		none

Description: MEMBOT is used to read or set the bottom of system RAM, pointed to by MEMSTR ($A05). This call is included in the C128 for completeness, but neither the Kernal nor BASIC utilizes MEMBOT since it has little meaning in the backed memory environment of the C128. Nonetheless, set the carry status to load MEMSTR into .X and .Y, and clear it to update the pointer from .X and .Y. Note that MEMSTR references only system RAM (RAM0). The Kernal initially sets MEMSTR to $1000 (BASIC text starts here).

EXAMPLE:

	SEC
	JSR	$FF9C	;get bottom of user RAM0
	INY
	CLC
	JSR	$FF9C	;raise it 1 block