If you are looking for the list of syscalls, see Category:Syscalls instead.
Most of the addresses on the table of system calls are entry-points to functions, but some of the addresses point to data like glyph tables.
A list of the known syscalls that correspond to functions is available here.
To access a system call, code should jump to 0x80020070 with the syscall number in register R0. After the syscall is executed, it will jump back to the calling code.
MOV.L syscall_number, R0 MOV.L #H'80020070, R2 JMP @R2 NOP NOP ; execution will resume here
The NOP after the JMP is necessary because in the SH-4 instruction set, JMP is a delayed branch instruction (the instruction after the JMP will execute before the jump occurs). The second NOP could really be anything (your code).
The numbers for the syscalls are documented on the Wiki page for each one. Note that the syscalls documented, and their numbers, refer to the Prizm models (fx-CG10 and fx-CG20), not the fx-9860G and alikes! Some syscalls have corresponding versions in the CASIOWIN that runs on these previous models, but others are new and others have changed behavior.