Hi I am aware that there is already a post about this but that seemed too confusing to me so i thought id explain in more detail.
1.Firstly open up microsoft notepad then leave it alone for the mo'
2. Write down the name of the rom that you want to create a .sav file for. U MUST WRITE THE ROM NAME EXACTLY AS IT IS
3.Open notepad again and press save as (you dont need to put anything in this)
4.write the rom name into the save name and at the end change the .gb/.gbc to .sav tip*save this to the desktop
5.below the name of the file change the format from *.txt to all files
6. Find this file on the desktop and move it to where the roms are on youre psp u know psp/game/rin
I am aware that homer has released v1 of his rin that has a state save but i found that a bit buggy
hope it helps and remeber if u have a rom caled acb.gbc (example) u chang the name to acb.sav pm me if you have trouble
i have to credit JJpotter as he sed this stuff first but it wasnt very clear link Saving Games With GBC Emulator (Guide)