Memory

The memory of the BELLE-ISA is word addressed, and features a call stack that is defined by the user.

Similar to many Von Neumann machines, the program memory and data are all part of the same “memory” on the machine.

When a program is loaded into memory, the .start, .ssp, and .sbp directives will be ignored. All other instructions will be loaded one after another, based on where the .start directive is located.

The entire memory of the machine contains 65536 addresses, starting from 0 to 65535.

There is also a call stack in the memory.

Call stack

The memory of the BELLE-ISA features a call stack, defined by a stack and base pointers, each of which point to an actual memory address that holds a value.

The call stack is bi-directional, meaning it can expand from both low to high addresses and high to low, depending on the positions of the stack and base pointer relative to each other.

The call stack by default will expand from a high to low memory address, and by default the stack and base pointers are set to 99.

If both the base and stack pointer are the same, the call stack will expand downwards, unless the base and stack pointers were changed after the stack had went upwards. Then, the stack will expand upwards unless the stack pointer is explicitly less than the base pointer.