Cs8900: Low Cost, High Performance Ethernet Controller For Non-Isa Systems; The Cs8900 Architecture; Isa Bus; Cs8900 In Io Mode - Cirrus Logic CRYSTAL LAN CS890 Technical Reference Manual

5.0 CS8900: Low cost, high per-
formance Ethernet Controller
for non-ISA systems
The CS8900 includes a direct interface
to the ISA bus. At the same time, the
CS8900 offers a compact, efficient, and
cost-effective, full-duplex Ethernet so-
lution for many non-ISA architectures.
The purpose of this application note is to
illustrate how to interface the CS8900 to
non-Intel and non ISA systems.

5.1 The CS8900 Architecture

The CS8900 is a highly integrated Eth-
ernet controller chip.
digital logic, RAM and analog circuitry
required for an Ethernet interface. This
high level of integration allows a prod-
uct designer to design an Ethernet inter-
face in 1.5 square inches of space on a
printed circuit board. The CS8900 has a
powerful memory manager that dynami-
cally allocates the on-chip memory be-
tween transmit and receive functions.
The on-chip memory manager performs
functions in hardware that are many
times done by software. This reduces
loading on the CPU and on the bus con-
nected to the CS8900. In fact, for 10
Megabit Ethernet, the CS8900 is the
highest throughput solution in the mar-
ket.
The integration of the analog transmit
waveform filtering makes it easier to
design a board that will pass EMC test-
ing. When the analog filters are exter-
nal, the PCB traces have fast edge
digital waveforms coming out of the
IC's 10BASE-T transmitter. The pres-
ence of high frequency energy in the fast
AN83REV1
It includes the
CS8900 Technical Reference Manual
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 CS8900 are in-
ternally filtered with a 5th order Butter-
worth 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.

5.1.1 ISA bus

An ISA bus is a simple, asynchronous
bus that can easily be made to interface
to most synchronous or asynchronous
buses. An ISA bus has separate address
and data lines as well as separate control
lines for read and write. ISA supports
IO address space of 64K bytes and
Memory address space 32 Mega bytes..

5.1.2 CS8900 in IO mode

When the CS8900 is used in an IO
mode, it responds in the IO address
space of the ISA. The CS8900 responds
to an IO access when
♦ Either of the bus IO command lines
(IOR* or IOW*) is active,
♦ The address on bus signals SA[0:15]
matches the address in the CS8900
IO base address register, and
♦ Bus
signals AEN,
TEST*, SLEEP* and RESET are in-
active.
All other control signals are ignored for
the IO operation.
REFRESH*,
71