In this paper the phonetic and speech corpus DIMEx100 for Mexican Spanish is presented. We discuss both the linguistic motivation and the computational tools employed for the design, collection and transcription of the corpus. The phonetic transcription methodology is based on recent empirical studies proposing a new basic set of allophones and phonological rules for the dialect of the central part of Mexico. These phonological rules have been implemented in a visualization tool that provides the expected phonetic representation of a text, and also a default temporal alignment between the spoken corpus and its phonetic representation. The tools are also used to compute the properties of the corpus and compare these figures with previous work.