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SMSC LAN91C111 32/16/8-Bit Three-In-One Fast Ethernet Controller
SMSC AN 9.6 7 Revision 1.0 (08-14-08)
APPLICATION NOTE
3.4.2 Signal Connection with Asynchronous Interfacing
Figure 3.2 Asynchronous Interface Connection
3.5 Synchronous Interface (VL-Bus)
The LAN91C111 also supports a 32-bit synchronous interface. This interface is intended to duplicate
the VESA standard (www.vesa.org
), otherwise known as the VL-Bus. Since this interface is not as
widely understood as the ISA bus we will go over this interface in some detail in this document. The
purpose of this discussion is not to necessarily duplicate a VL-Bus but to better explain the use of the
control signals and requirements to support a synchronous interface. With this information a design
engineer should be able to successfully interface the LAN91C111 to any generic synchronous bus
interface. All registers except the DATA REGISTER will be accessed using byte or word instructions.
Accesses to the DATA REGISTER could use byte, word, or double word (dword) instructions.