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STP2002QFP
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
Sun Microsystems,
5.4 Programmer’s Reference

5.4.1 Overview

During normal operation, the software-to-hardware interaction is primarily
performed via the host memory data structures, with a minimal command/sta-
tus handshake (less than one interrupt per packet). Software intervention is re-
quired for initialization of the hardware after resetting the channel, for
network management, for error recovery, and for diagnostic purposes. Local
FIFOs’ data structures and most of the registers are invisible to the software,
except for diagnostic purposes.

5.4.2 Host Memory Data Structures

The host memory data structures are organized as wrap-around descriptor
rings of programmable size. The transmit and receive data structures are very
similar, except for three major differences:
1. Descriptor layout
2. Number of descriptors per packet: one for receive, unlimited for
transmit
3. Data buffer alignment restrictions: none for transmit, one for
receive
Programming Note: The pointers to descriptor ring base addresses
must be 2K-byte aligned.