Cirrus Logic AN83 - Manual (Page 7)

AN83
AN83REV3 7
gram and read the CS8900A control and status reg-
isters, and how to transfer user data between the
CS8900A and the PC main memory via the ISA
bus. On the NOS side, the drivers provide the stan-
dardized services and functions required by the
NOS, and hide all details of the CS8900A hardware
from the NOS. The EEPROM device programs the
CS8900A whenever the a hardware reset occurs,
and call also store state/configuration information
for the driver.
Cirrus’s Software Driver (
&U\VWDO /$1Œ) Distribu-
tion Policy is as follows. The CS8900A developer
kit contains a single-user copy of object code which
is available only for internal testing and evaluation
purposes. This object code may not be distributed
without first signing a LICENSE FOR DISTRIBU-
TION OF EXECUTABLE SOFTWARE, which
may be obtained by contacting your sales represen-
tative. The LICENSE FOR DISTRIBUTION OF
EXECUTABLE SOFTWARE gives you unlimit-
ed, royalty-free rights to distribute Cirrus-provided
object code.
HARDWARE DESIGN
This section give design guidance for both embed-
ded and adapter card designs, including recommen-
dations for dealing with the upper ISA address lines
(LA[20:23]), choosing transformers, and laying out
the board.
CS8900A: CONNECTING TO NON-ISA
BUS SYSTEMS
The CS8900A includes a direct interface to the ISA
bus. At the same time, the CS8900A offers a com-
pact, efficient, and cost-effective, full-duplex
Ethernet solution for non-ISA architectures. The
purpose of this section is to illustrate how to inter-
face the CS8900A to non-Intel and non ISA sys-
tems. Design examples include the MC68302,
Cirrus Logic CL-PS7211 ARM and Hitachi SH3.
The CS8900A Architecture
The CS8900A is a highly integrated Ethernet con-
troller chip. It includes the digital logic, RAM and
analog circuitry required for an Ethernet interface.
This high level of integration allows a product de-
signer to design an Ethernet interface in 1.5 square
inches of space on a printed circuit board. The
CS8900A has a powerful memory manager that dy-
namically allocates the on-chip memory between
transmit and receive functions. The on-chip mem-
ory manager performs functions in hardware that
are many times done by software. This reduces
loading on the CPU and on the bus connected to the
CS8900A. In fact, for 10 Megabit Ethernet, the
CS8900A is the highest throughput solution in the
market.
The integration of the analog transmit waveform
filtering makes it easier to design a board that will
pass EMC testing. When the analog filters are ex-
ternal, the PCB traces have fast edge digital wave-
forms coming out of the IC’s 10BASE-T
transmitter. The presence of high frequency energy
in the fast edges causes major problem during EMC
tests, such as FCC Part 15 class (B) or CISPR class
(B). The 10BASE-T signals driven out of the
CS8900A are internally filtered with a 5
th
order
Butterworth filter and the signals lack fast edges.
Lack of high frequency signals makes it straight
forward to design a card that meets FCC class (B)
or even CISPR class (B) requirements.
Applications
Operating System Software
e.g., File Manager
Network Operating System
e.g., Novell or Microsoft
CS8900 - specific device drivers:
e.g., NDIS & ODI compatible drivers
CS8900 Registers & Memory EEPROM
Figure 2. Software Application Summary