Commodore 128 Programmer's Reference Manual page 430

420 COMMODORE 128
RESULTS:
Registers:
Memory:
Flags:
EXAMPLE:
SEC
JSR $FF99
DEY
CLC
JSR $FF99
.X = lsb of MEMSIZ
.Y = msb of MEMSIZ
MEMSIZ ($A07)
none
;get top of user RAMO
;lower it 1 block
MEMTOP is used to read or set the top of system RAM, pointed to by
MEMSIZ ($A07). This call is included in the C128 for completeness, but neither the
Kernal nor BASIC utilizes MEMTOP since it has little meaning in the banked
memory environment of the C128 (even the RS-232 buffers are permanently
allocated). Nonetheless, set the carry status to load MEMSIZ into .X and .Y, and
clear it to update the pointer from .X and .Y. Note that MEMSIZ references only i j
system RAM (RAMO). The Kernal initially sets MEMSIZ to $FF00 (MMU and
Kernal RAM code start here).
10. $FF9C MEMBOT ;set/read bottom of system RAM
PREPARATION:
Registers:
Memory:
Flags:
Calls:
RESULTS:
Registers:
Memory:
Hags:
EXAMPLE:
SEC
JSR $FF9C
INY
CLC
JSR $FF9C
.X = lsbofMEMSTR
.Y = msbofMEMSTR
system map
.C = 0 -> set bot of memory
.C = 1 —> read bot of memory
none
.X = lsbofMEMSTR
.Y = msbofMEMSTR
MEMSTR ($A05)
none
;get bottom of user RAMO
iraise it 1 block
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