A data transfer control device and an electronic instrument which can implement a process to be made on data transmitted and received through a high speed bus on a circuit operating at a low frequency. The data transfer control device has a conversion circuit which converts K-bit width data transferred at a frequency FC1 (in USB 2.0 HS mode) through a bus into data having an L-bit width (LK) by rearranging, and a processing circuit which receives the L-bit width data from the conversion circuit and carries out a K-bit based process on an L-bit basis at a frequency FC2 lower than FC1. This enables to perform the K-bit based process at the low frequency FC2. Configuration on a transmission end can be implemented in the same manner. The transfer data in the USB 2.0 HS mode is processed on the L-bit basis while the transfer data in the FS mode is processed on the K-bit basis. The present invention is applicable also to the process on data transferred through a bus under the IEEE1394 or SCSI.