CS8900A Ethernet Controller

Crystal Semi's CS8900A-CQ

___This is the chip that makes it all possible. Produced by Crystal Semiconductor -- a division of Cirrus Logic -- the CS8900A includes on-chip RAM, 10baseT transmit and recieve filters, and a direct ISA bus interface with 24mA drivers. The CS8900A is available in a 100-pin TQFP package - ideally suited for small form-factor, cost-sensitive ethernet applications. With the CS8900A, system engineers can design a complete ethernet circuit that occupies less than 1.5 sqaure inches (10 sq. cm) of board space.

Valor's ST7011T

Data Sheets

___The ST7011T (or ST7010, as the case may be) is a 10baseT transformer. Its job is to modify the ethernet signals being produced by the CS8900A, so that they are recognized by whatever devices are at the other end of the cable. The CS8900A produces signals at what is know as TTL level, that is, they are bursts of 5 volt electrical energy. While this particular level of electricity is perfect for signaling other ICs on a circuit board, it is extremely unsuitable for communication over a distance. The ST7011T solces this problem by converting the signals in a way that they are just right for UTP Cat. 5 cabling, at distances of up to 100 meters (roughly 300 feet). Please not, that this particular transformer is only capable of producing 10baseT output, and those wishing to use AUI or BNC style ethernet may need to wait for another option.
___The Valor ST7011T is becoming particularly troublesome to source. If I'm unable to find a supplier that can sell us this chip, we'll be forced to find an alternative. Rhombus also produces 10baseT transformers, though they are equally difficult to find. This may be a good excuse to find a transformer capable of 10base5 and 10base2 output, in addition to twisted pair. Suggestions are most welcome.