Data processing system for transmitting data between a host processor and an I/O device

In a data processing system transmitting data from a host processor to an I/O device controlled by a control unit having an address wherein the data is being transmitted in a WRITE operation, an apparatus comprising:

• I/O means in said host processor for starting said WRITE operation by transmitting a WRITE command, the address of the control unit of said I/O device, and data;
• local channel control means connected to said host processor for receiving said WRITE command, said address and said data transmitted by said I/O means, said local channel control means having look up means for looking up a first command-accepted status and sending said first command-accepted status to said I/O means dependent on the value of said address and the WRITE command, said first command-accepted status for indicating that said WRITE command was received, said remote channel control means further including first transmitting means for transmitting therefrom said WRITE command, said address and said data;
• remote channel control means connected to said local channel control means for receiving said WRITE command, said address and said data transmitted from said first transmitting means, said remote channel control means including second transmitting means for transmitting said WRITE command and said data to the control unit identified by said address;
• said control unit being connected to said remote channel control means for receiving from said second transmitting means said WRITE command and said data, said control unit further having status means for sending a second command-accepted status to said remote channel control means after the receipt of said WRITE command from said remote channel control means;
• said remote channel control means having remote status means for sending a third command-accepted status to said local channel control means after the receipt of said second command-accepted status from said control unit;
• said local channel control means having local status means for sending a channel-end status to said host processor after the receipt of said third command-accepted status from said remote channel control means;
• and
• disconnect means in said I/O means for disconnecting said local channel control means form said host processor after the receipt of said channel-end status from the local status means of said local channel control means.

In a data processing system transmitting data from an I/O device controlled by a control unit having an address to a host processor wherein the data is being transmitted in a READ operation, an apparatus comprising:

• I/O means in said host processor for starting said READ operation by transmitting a READ command and the address of the control unit of said I/O device;
• local channel control means connected to said host processor for receiving said READ command and said address transmitted by said I/O means, said local channel control means including a look up means for looking up an initial status and sending said initial status to said I/O means dependent on the value of said address and said READ command, said remote channel control means further including first transmitting means for transmitting therefrom said READ command and said address;
• said I/O means having disconnect means for disconnecting said local channel control means from said host processor after the receipt of said initial status from said the look-up means of said local channel control means;
• remote channel control means connected to said local channel control means for receiving said READ command and said address transmitted from said first transmitting means, said remote channel control means including second transmitting means for transmitting said READ command to the control unit identified by said address;
• said control unit being connected to said remote channel control means for receiving from said second transmitting means, said READ command, said control unit also having status means for sending a first command-accepted status to said remote channel control means after the receipt of said READ command from said remote channel control means, and said control unit further being connected to said I/O unit and having means for receiving data from said I/O unit after receiving said READ command from said second transmitting means and for transmitting said data to said remote channel control means;
• said remote channel control means having remote status means for sending a second command-accepted status to said local channel control means after the receipt of said first command-accepted status from said control unit, and having means for sending said data from said control unit to said local channel control means;
• and
• said local channel control means having local connect means for connecting said local channel control means to said host processor after the receipt of said second command-accepted status from said remote channel control means, and further having data transfer means for transferring said data from said remote channel control means to said host processor after said local connect means has connected said local channel control means to said host processor.