Matrox Meteor-II /1394 69
The physical layer (PHY) is part of a bi-directional interface between the link layer (Link) and the actual IEEE 1394 serial bus. The physical layer acts as a converter, reformatting the commands and digital data it receives, so that the data can be transmitted over the serial bus. The PHY monitors the line conditions to determining connection status, for initialization and arbitration, and for packet reception and transmission. The physical layer supports data transmission rates of up to 400 Mbits per second.
The link layer (Link) is the second component in the bi-directional interface between the physical layer (PHY) and PCI bus. The Link is a PCI-to-1394 Host controller and is compliant with both PCI and 1394 OHCI specifications. The link layer supports both asynchronous and isochronous data transfer between nodes. When transmitting packets, the Link must send a request to the PHY, which controls the direction of transmission between the two layers. The link layer also controls the transfer speed between itself and the PHY, and supports data transfers of 100, 200, or 400 Mbits per second. In addition, the Link is capable of transferring a cacheline of data at 132 MBytes per second over the PCI bus after connecting to the memory controller on the Host. In order to overcome high or long PCI latency, the link layer also provides deep FIFOs.
The optional galvanic isolation barrier isolates the Matrox Meteor-II /1394’s ground from that of the 1394 network. For example, 1394 network could consist of several PCs, or other devices such as a digital television or digital VCR. If each device in the network has a different ground, a potential difference is created across them; this situation is called a ground loop, and can eventually lead to loss of data, or even damage to system components. If a power surge occurs, the circuit tries to ground excess power, but the Matrox Meteor-II /1394 would be protected because its ground is isolated from the rest of the network.
