Part 1.
Clears everything
ACLS
each background layer
DIM BG0[16383]
DIM BG1[16383]
DIM BG2[16383]
DIM BG3[16383]
loads each layer
LOAD "DAT:SC_MAP_L0",BG0,0
LOAD "DAT:SC_MAP_L1",BG1,0
LOAD "DAT:SC_MAP_L2",BG2,0
LOAD "DAT:SC_MAP_L3",BG3,0
Part 2.
sets the size
BGSCREEN 0,64,64
BGSCREEN 1,64,64
BGSCREEN 2,64,64
BGSCREEN 3,64,64
puts it all on the screen
BGLOAD 0,BG0
BGLOAD 1,BG1
BGLOAD 2,BG2
BGLOAD 3,BG3