Well, coming from a Chinese family and as our family cook rice everyday...
The short answer is yes - you will be able to cook 1 cup with the 5.5 cup model. the problem is, though you will be able to cook much smaller volume in a large cooker -- you will have rice covering the pan, a thin layer above bare metal[1]. Scooping up rice from it is a OK, but you will tend to 'fold' the rice in order to put it in a bowl which kind of affect the texture of the rice - if you use a smaller one you will get rice in a nice, cylinder shaped from which you can get a nicer scoop which is naturally formed by expansion of rice and steam.
[1] This has become much better with all these rice cooker armed with circuits (as in your case) which slowly, but accurately cook every grain of rice you put in -- albeit at a much longer time. the cooking time with old, traditional kind of rice cooker is ~ 30 min for 2 cup of rice whereas the newer, logic-equipped device will need ~1 hour for cooking - but of course the quality is much better