Assuming that the company has several developers, then a CTO may be minimal coding, but he should be able to come in when needed. I have worked for a CTO that was exceptional, but he didn't work in Java, as his languages were LISP and C, so he didn't do any coding, but he had fantastic architects under him that were exceptional mentors and coders, so he worked on the big picture and kept everything going, while getting whatever resources were needed by the developers or anyone else in the tech area.
In a smaller company it may be that the direction goes into a language that the CTO doesn't know, but if he feels comfortable managing, and has a very strong understanding of architecture and is an exceptional hacker, so can recognize excellence when he encounters it, then he may do minimal, if any coding.
For example, you start a solution using .NET and ASP. You then decide that F# may be a better choice, using ASP, then you switch over to Scala and LIFT. It is unlikely that the CTO would have time to learn the new language quickly, with everything on his plate, but over time he should become familiar with it, but he can find people that know the language and can do the mentoring of other developers.
In a very tiny company a CTO should do coding as there may only be 2 or 3 developers and he will be the architect/senior developer/project manager, so a CTO that can't code in the language is almost useless in trying to finish the language, as he isn't earning his pay, IMO.