An205 – Cirrus Logic AN205 User Manual
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AN205
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13) In the sample connection diagrams I see SHBE# and AEN connected to a chip select from the pro-
cessor. Also, only 3 address lines are connected. Why?
Let's cover this one at a time.
SBHE# must toggle to put the CS8900A into 16-bit mode. SBHE# is guaranteed to toggle when
connected to CS#. It will always be low during a read or write of the CS8900A. This also means that
you can only do 16-bit reads or writes. No 8-bit accesses.
AEN can be used as an active low chip select when DMA is not used.
When the CS8900A powers up with no EEPROM, it defaults to I/O Mode with a Base Address of
0x0300. This is why address lines [A9:A8] are tied high.
So, the CS8900A always sees 0x30x on its address lines. Reads and writes are gated by using AEN as
a chip select.
Since accesses are always 16-bit how does the CS8900A handle odd length frames?
When sending an odd length frame, the software will still “bid” for the odd number of bytes. Software
will do (frame bytes + 1)/2 16-bit writes to the CS8900A. The CS8900A will ignore the extra byte.
When reading an odd length frame, the software will do (frame bytes + 1)/2 16-bit reads. Software will
pass the correct frame length to the upper layer. The upper layer will ignore the extra byte.
14) How do I program the EEPROM connected to the CS8900A?
You can download a sample program from the CS8900A drivers page. Go to the Cirrus web site,
. Download mfg.zip.
15) The spec defines VIXH (page 111, XTAL1 input high voltage when operating with external clock)
as 3.5 Volt min. I presume this is for a VDD of 5V. What is VIXH for a VDD of 3.3V?
The spec for 3.3 V operation is 2.4 V.
16) Where can I get pricing and availability information for the CS8900A Integrated Circuit or the
CRD8900A-1 Evaluation Board kit?
You can contact Cirrus Sales for pricing and availability information at
ou can also request a sample by going to
and follow the directions on screen.
17) I have ordered the CRD8900A-1 kit and would like the data sheets/specifications for this reference
board. Where can I locate them?
Information on the Cs8900A reference design board is in the application note, Crystal LAN
™
CS8900A
Ethernet Controller Technical Reference Manual, (AN83) at
ting on page 15.
18) We received CS8900A-IQ, through a distributor, in moisture sealed packaging. There was no
JEDEC Moisture Level markings on the package. Is there a moisture sensitivity rating?
This product is qualified at the JEDEC Level III.