Method of time stamping to enable device bridging over dissimilar buses
View Patent ↗Several local IEEE1394 buses are bridged together over a second bus type to create a global bus wherein each local bus node is able to address nodes across the global bus without the local nodes being aware of the bridging operation. A bridging device operates by translating local bus node addresses to a global bus for communication over the second bus type. Alternatively, the local bus node identification process is controlled by the bridging device operating as the root node to cause the local nodes to be identified with a node address that is unique for the global network. The second bus type operates as a backbone for the global network and can be any type of communication bus or network with capability to transport the local bus traffic. The bridging devices that interface the local IEEE1394 buses to the backbone contain portals specific to each bus type that can communicate data between the dissimilar buses.
1. A method of bridging devices from a first data bus type over a second data bus type using a bridge device comprising a portal connected to the first data bus type and a portal connected to the second data bus type the bridging method comprising the steps of:
assigning local addresses to devices connected to the first data bus type;
assigning unique global addresses recognized by the second data bus type to devices connected to the first data bus type;
mapping between the local addresses and the global addresses to form a map table;
translating between global addresses and local address using the map table when bridging communication from devices connected to the first data bus type over the second data bus type;
in a transmitting bridge device, removing a time stamp associated with the first data bus type and adding a time stamp associated with the second data bus type to a message transmitted; and
in a receiving bridge device, removing the time stamp associated with the second data bus type from the message transmitted and adding a time stamp associated with the first data bus type.
2. A method of bridging IEEE-1394 devices that are not bridge aware from one IEEE-1394 bus branch through a backbone bus to another IEEE-1394 bus branch, each IEEE-1394 bus branch having a bridge device comprising an IEEE-1394 portal and a backbone portal, the bridge device having control over IEEE-1394 devices in the branch, the method comprising the steps of:
(a) assigning a cycle master (CM) to control the backbone bus;
(b) assigning a backbone bus node number to other backbone nodes;
(c) the CM requests a first bridge device to initiate a bus configuration, the bridge device performing the sequence comprising:
resetting each IEEE-1394 device; tree-identification of IEEE-1394 devices;
self-identification of IEEE-1394 devices controlled by a branch root node, the self-identification comprising a physical-identification;
collecting self-identification packets in the branch root node;
transmitting the collection of local self-identification packets to the CM;
(d) forming a database of self-identification packets from all nodes in the network;
(e) accumulating and transmitting the database of self-identification packets to a second bridge device;
(f) the CM requests the second bridge device to initiate a bus configuration wherein the IEEE-1394 portal becomes the branch root node; the root node causes the received database of self-identification packets to be transmitted to all local nodes in the branch causing the local nodes to begin self-identification at an address above the highest address in the received database; the local nodes transmit self-identification packets;
(g) accumulating into the database the self-identification of the local nodes and transmitting the accumulated database to a third bridge device;
(h) repeating steps (f) and (g) for all branches connected to the backbone network, wherein the third bridge device of step (g) becomes the second bridge device of step (f);
(i) the CM send an accumulated self-identification database to all branch root nodes; each branch root re-transmits self-id packets from branch 0 and branches with higher branch numbers;
in a transmitting bridge device, removing a time stamp associated with the IEEE-1394 bus and adding a time stamp associated with the backbone bus to a message transmitted; and
in a receiving bridge device, removing the time stamp associated with the backbone bus from the message transmitted and adding a time stamp associated with the IEEE-1394 bus; whereby each local node address is unique and is part of a single logical bus.