An205 – Cirrus Logic AN205 User Manual
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AN205
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19) Where can I find drivers for the CS8900A?
Our CS8900A drivers are available on the Internet at:
20) I'm connecting the CS8900A to a big endian processor and have switched the high and low order
byte connections (D8:15 -> D0:7 and D0-7 -> D8:15). I want to be sure that I maintain byte order
when doing a memory space transfer of packets, but require byte swapping when writing to the con-
trol registers on the ethernet controller.
The CS8900A assumes a little-endian ISA-type system. However, network byte order is always big-
endian. Therefore to minimize software manipulation of frame data in ISA systems, the CS8900A
byte-swaps frame data internally. The control and status registers are not byte swapped.
In a big-endian system (for example., Motorola) you can either byte-swap the network data (to reverse
the byte swapping done internally to the CS8900A in software or you can do it in hardware (byte swap
the data lines to the chip). Byte swapping the data lines is much more efficient; you will only need to
byte swap the control/status/counter values in software and not the frame data. (Most of the read/writes
to the chip are frame data.) Since network byte order is always big endian this scheme works without
special support on the other end of the network.
21) I want to make an embedded system with the CS8900A using 8-bit mode. Do you have some generic
C code available with examples of polling mode?
We have a demonstration driver CS8900DemoDosV11.zip available at our web site at:
the VxWorks driver with source code.
Porting to 8-bit mode is the customer’s responsibility.
22) What is the simplest way of getting my CS8900A up and running if I am using an embedded ethernet
application?
Download our loop.zip file at
ad the
readme
file first to get instructions on how to construct a loopback connector and run this file. Please
note that for external loopback mode to work you may need to set the full duplex (fdx) bit in testCTL
register. This approach should give you simple receive and transmit capability with the CS8900A using
the embedded processor of your choice, such as one of the Cirrus Logic EP73XX family of embedded
processors.
23) The schematics in the application notes show that there are .01 uF, 2 kV capacitors going pins 15
and 10 of the transformer to ground. These parts are marked DO NOT STUFF. Is the purpose of
these caps to prevent EMI / ESD emissions/susceptibility?
It's there to help EMI issues. The reason for the 2 KV rating is that the side of the transformer should
withstand 1500 Vrms for 1 minute. Also, it is OK to substitute .01 uF caps instead of .1 uF caps. The
only required capacitor is on pin 7, the center tap for TX+/-.
24) I can get a link with a 10Mb hub, but I get no link with a 10/100Mb hub or switch.
Clear bit 9, AutoAUI/10BT, in the LineCTL register. Here’s what is happening: When the
AutoAUI/10BT bit is set, the CS8900A waits for signal on either the AUI port or the 10BaseT port. It