A reprogrammable subscriber terminal of a subscription television service which can have the control program code of its control processor modified by downloading new program code from the headend. The control processor stores a boot program in an internal read only memory. Upon start up and resets, the boot program determines whether the control program should be changed from a command sent from the headend. The command, termed a parameters transactions, includes the number of expected download program code transactions required to complete the control code modification, the memory space areas where the code is to be loaded, and the channel over which the download program code transactions are to be transmitted. The channel is tuned and when the boot program receives all the download program code transactions accurately and stores them, the boot program will cause the control program to be restarted at a selected address of the new or modified control program code which has been downloaded. The boot program may download code to different configurations of subscriber terminals including those with Flash EPROM or extended memories from plug-in expansion modules.