JPS6465654A - Channel control system - Google Patents

Abstract

PURPOSE:To attain the set up of plural modes included in a bus from the external and to prevent the generation of overrun, by providing the title system with a transfer mode storing means, a channel device specifying means, a comparing means, a transfer mode selecting means, and so on. CONSTITUTION:When a request signal is inputted from one of channel devices 8 to the channel device specifying means 2, the means 2 specifies a sender equipment 8 stored in a transfer mode data storing means 1 and reads out maximum data width to be transferred by the equipment 8. Then, the comparing means 3 decodes the data width of the requested transfer mode in the request signal and compares the decoded result with the data width obtained from the means 1. When the data width of the requested transfer mode is less than the maximum data width as the result of the comparison of the means, the transfer mode selecting means 4 selects the data width of the requested transfer mode, and in the other case, selects the maximum data width. Thus, data access can be controlled from the equipment 8 through a memory access control part 5, so that a transfer mode can be set up from the external and the generation of overrun can be prevented.