Register parameters
RST 20H, DEFB $54
IN: A = 0, always BC = requested size of reserved memory in bytes (2 to 256) IX = memory handle (returned from OS_Mop) OUT, if call successful: Fc = 0 HL = address of memory allocated (H14 & H15 are memory mask) B = bank number of allocated memory C = segment specifier implied by HL (H14 & H15) OUT, if call failed: Fc = 1 A = error code: RC_HAND ($08), IX is not a valid memory handle RC_ROOM ($07), no room to allocate block in MEMORY POOL RC_ERR ($0F), if BC > 256 bytes, fatal error Registers changed after return: ....DE../IXIY same AFBC..HL/.... different
Notes
Remember "No Room" means the pool is exhausted, and not the whole of memory. If a subsequent OS_Mop cannot allocate a pool, then memory is definitively exhausted.
The call WILL NOT automatically bind in the allocated memory into the Z80 address space.
Related calls
OS_Bix, Bind in extended address
OS_Box, restore bindings after OS_Bix
OS_Fc, select fast code (fast bank switching)
OS_Mcl, close memory (free memory pool)
OS_Mfr, free (previously allocated block) memory
OS_Mgb, get current bank binding in segment
OS_Mop, open memory (allocate memory pool)
OS_Mpb, set new bank binding in segment
OZ_Mgb, get current bank binding in segment
OZ_Mpb, set new bank binding in segment