Method and apparatus for bi-directionally transferring data between an ieee 1394 bus and a device to be controlled by a control signal transmitted via the bus

Abstract

The IEEE 1394 bus communication protocol has three layers: physical layer, link layer, and transaction layer. Typically, the transaction layer is realized by firmware whereas the other layers are implemented using chip sets. The link layer IC usually contains a FIFO having a capacity of e.g. 32k or 64k bits. Therefore, the link layer chip is the most costly part of a complete IEEE 1394 interface. Due to these cost reasons most ICs on the market are not bi-directional although the IEEE 1394 bus specification supports this feature. Incoming or outgoing data packets are intermediately stored in the FIFO. The current solution to this problem is to have two separate IEEE 1394 bus nodes assigned to the same application, the two nodes including two physical layer ICs and two link layer ICs. The inventors have found that although the physical link layer interface is not designed for this purpose, it works correctly with up to three link layer ICs and one physical layer IC if the additional link layer IC/ICs is/are programmed respectively. Therefore two or more link layer ICs can operate together with one physical layer IC in one node wherein the link layer ICs are connected to the same application or device.