Cartridge code (193 chars):

p=pget
cls(1)n=126m=127
rule="0111100"
::e::
for i=0,m do
c=pget(i+1,n)
c+=pget(i,n)*2
c+=pget(i-1,n)*4
d=0
c=7-c
if(sub(rule,c,c)=="1")d=1
pset(i,m,d)
end
memcpy(24512,24576,8192)flip()
goto e