Build tool/InstallRAMISR

Build tool option InstallRAMISR is used to automatically select RAM in page 0 then copy data there at startup, so ROM cartridge can take advantage of (almost) 16 KB of additional RAM.

As page 0 (addresses 0x0000-0x3FFF) is the place where MSX will search for interruption handler (ISR), the build tool will automatically copy the selected ISR (see CustomISR option).

InstallRAMISR can take 3 values:

• RAM0_NONE: Don't switch page 0 to RAM
• RAM0_ISR: Switch page 0 to RAM then install ISR at 0x0038 (mandatory address)
• RAM0_SEGMENT: Switch page 0 to RAM, install ISR at 0x0038 , then copy segment data (for mapped-ROM)

RAM0_SEGMENT

When using RAM0_SEGMENT option, you can define a source code file named {projectName}_p0.c (or .asm) and it will be automatically added to your mapper data and copy at statup in page 0. Code and data from your _p0 file will be available starting from address 0x0100 (after the ISR) so you have a little less than 16 KB available in page 0 (16 KB - 0x100 = 16128 bytes).

_p0 will be place in segment after your main program. Segment number depend of the mapper format your are using:

Mapper	Segments
ASCII-8	#4 and #5
ASCII-16	#2
KONAMI K4	#4 and #5
KONAMI K5 (SCC)	#4 and #5
NEO-8	#6 and #7
NEO-16	#3

When you use this option, these segments are reserved for code and data to be copied on page 0 and cannot be used for anything else.