In a data processing system in which encoded data is transferred by a peripheral control unit between a central processing unit and one or more peripheral devices, method and apparatus for selecting and enabling one of a plurality of translators in the peripheral control unit to translate the encoded data from one code to another. Prior to transferring the encoded data between the central processing unit and the peripheral device, the central processing unit issues a command which contains an identification code word identifying the translator to be enabled. Each translator stores its own distinctive translator code word and each of these translator code words are successively compared with the identification code word until a match is obtained. When a match is obtained, the translator associated with the matching translator code word is enabled, and the encoded data is applied to the enabled translator for translation. In this manner, the peripheral control unit self-determines its translation capabilities and, for a given data transfer, enables the appropriate translator.