Method for exchanging messages between a shared memory and communication adapters using an efficient logical protocol

Claim 1

A method for receiving interleaved bursts of messages sent from a plurality of communication adapters (20) to which are attached different users (22) to a shared memory subsystem (10) comprising a depository storage (12) and managing means (14) for managing said depository storage, said adapters being connected to the shared memory subsystem (10) by a bus (30) comprising data lines (30-d), address lines (30-a) and control lines (30-c) controlled by an arbiter (26), said messages being sliced into data bursts (57) of variable sizes, said method characterized in that it comprises the steps of: (a) providing a first unique data flow control line RBE (34) connecting said managing means (14) to all said communication adapters (20) and asserted by said managing means (14) to allow the sending of the data bursts from said adapters (20); (b) making a bus request to said arbiter (26) by communication adapters (20) that have messages to send to the shared memory subsystem (10); (c) generating a burst control word (52) associated to each data burst (57) to be sent by the communication adapters (20), said control word comprising at least the identification of the user (22) owner of the message; (d) sending a burst of data (50) to which is associated the corresponding control word (52) on said data lines (30-d) of bus (30) by one of the communication adapters (20) selected by said arbiter (26) with a unique address for all adapters on the address lines (30-a) to the subsystem (10); (e) reading said control word (52) by said managing means (14) to store the data burst in the depository storage (12) according to the identification of the user owner of the message.

Claim 4

A method for transmitting interleaved bursts of messages sent from a shared memory subsystem (10) comprising a depository storage (12) and managing means (14) for managing said depository storage, to a plurality of communication adapters (20) to which are attached different users (22), said adapters (20) being connected to the subsystem (10) by a bus (30) comprising data lines (30-d), address lines (30-a) and control lines (30-c) controlled by an arbiter (26), said messages being sliced into data bursts (57) of variable sizes, method characterized in that it comprises the steps of: (a) dequeueing a message from said depository storage (12); (b) sending a first control information indicating that a message is ready for transmission (MRX) to the concerned communication adapter (20) through the bus (30), said first control information comprising at least the identification of the user (22) to whom the message has to be transmitted on said data lines (30-d) with a special code on said address lines (30-a); (c) providing a second unique data flow control line XBE (36) connecting said managing means (14) to all said communication adapters (20) and asserted by said managing means (14) to allow said adapters (20) to request the data bursts from the shared memory subsystem (10); (d) making a bus request to said arbiter (26) by the communication adapters (20) that have messages to receive from the shared memory subsystem (10); (e) generating a second control information Transmit Burst Request (XBR) for requesting the transmission of a burst comprising at least the identification of the user and the maximum burst size of the requested data that can be processed by the adapter, said second control information (XBR) is sent on said data lines (30-d) of the bus (30) from the communication adapter (20) selected by the arbiter (26) with a unique address for all adapters on said address lines (30-a) to the subsystem (10); (f) fetching the requested data burst whose size must be below the maximum demanded by said adapter (20) in the depository storage (12) to store them temporarily in managing means (14); (g) providing third data flow control lines Transmit Burst Ready (XBY) (32) connecting said managing means (14) to each adapter (20) and asserted by managing means (14) to notify the concerned communication adapter (20) to read the requested data burst in managing means (14); (h) making a bus request to said arbiter (26) by the concerned communication adapters (20) that have messages to receive from to the shared memory subsystem (10); (i) sending a burst of data (50) to which is associated a burst control word (52) on said data lines (30-d) of said bus (30) by managing means (14) when said arbiter (26) has granted said bus (30), said control word (52) comprising at least the identification of the user owner of the data burst; (j) reading said control word by said adapter (20) to check if the data that follow correspond to the requested data burst to send that data burst to the destination user indicated in the control word; (k) sending a third control information End of Message (EOM) indicating if the complete message has been transmitted to the subsystem (10) by said adapter (20), said third control information comprising at least the identification of the user (22) to which the message has been transmitted and the notification of good or bad transmission.

Claim 6

The method according to claims 4 or 5 characterized in that the burst control word specifies: - the user owner of the data burst (53); - the size of the data burst (54); - the position of the burst in the message (55).

Claim 7

A method for exchanging messages comprising the receiving method according to claims 1 to 3 and the transmitting method according to claims 4 to 6 wherein the control flow of the messages exchanged between the adapters (20) and the shared memory subsystem (10) is managed by a microprocessor (16) provided in said subsystem, characterized in that it comprises the steps of: (a) sending a command (41) from said microprocessor (16) to a concerned communication adapter (20) through the bus (30), after said bus (30) has been granted by said arbiter (26), said command comprising at least the identification of said concerned adapter on said data lines (30-d) with a special code on said address lines (30-a); (b) answering back immediately a Response (42) by said adapter (20) on data bus (30-d) after the execution of the command to free said bus (30).