Data transfer unit for receiving general purpose commands when no expedited command is arriving

Abstract

A data transfer unit is provided which reliably receives the expedited command when the expedited command has arrived, and changes over the reception to receiving a general purpose command when no expedited command is arriving. The data transfer unit comprises: a data module (DAT MOD) having at least a command module (COMOD), and first and second interfaces (I/F); and first and second host control units (HC); wherein an expedited command output at an indefinite period from the first (HC) is fed to the DAT MOD through the first (I/F); the first (I/F) is turned off and the second (I/F) is turned on at all times when a general purpose command output at a predetermined period from the second (HC) is fed to the COMOD through the second (I/F); and the first (I/F) is turned on and the second (I/F) is turned off by (I/F) change-over signals of an active level fed to the DAT MOD just before the first (HC) produces the expedited command.

Dependencies are inferred from the claim text.