50
AN83REV1
CS8900 Technical Reference Manual
3.0 Jumperless Design
Using the CS8900, both add-in adapters
and motherboard solutions can be imple-
mented without hardware jumpers or
switches. The CS8900 and media access
control (MAC) device drivers obtain con-
figuration information directly from non-
volatile memory. For add-in ISA adapters,
a serial EEPROM will be connected di-
rectly to the CS8900 via the serial interface.
Motherboard solutions may use an on-
board serial EEPROM or other nonvolatile
memory such as a flash EPROM-based
BIOS. Typically, a separate software utility
is used to initially store and modify the
configuration information.
3.1 Serial EEPROM
Two types of configuration information is
stored in the EEPROM: configuration in-
formation automatically loaded into the
CS8900 after each reset and driver configu-
ration information used by the MAC driver.
3.1.1 Reset Configuration Block
After each reset (except EEPROM reset) the
CS8900 checks to see if an EEPROM is
connected. If an EEPROM is present, the
CS8900 automatically loads the first block of
data stored in the EEPROM into its internal
registers. This block of data is referred to as
the Reset Configuration Block. It is used to
initialize the CS8900 after each reset.
Software resets may occur frequently and
performance will be enhanced if chip re-
initialization takes as little time as possible.
Therefore, since EEPROM readout takes
approximately 25
µ
sec. per word, the
length of the Reset Configuration Block
should be kept to a minimum.
The MAC drivers provided by Crystal will
retain much of the adapter’s configuration
across software resets. Therefore, the only
information required in the Reset Configu-
ration Block when used with Crystal-
provided drivers will be the IO base address
(if different than the default 300h) and
Boot PROM configuration when a Boot
PROM is used.
Table 3.1 shows an example of a typical
Reset Configuration Block for an adapter
with a Boot PROM . The first word of the
block indicates the type of EEPROM in use
and the length of the Reset Configuration
Block (the number of bytes loaded into the
CS8900 after reset). The last word of the
block contains an 8-bit checksum (in the
high byte) of all the bytes in the block. Re-
fer to Section 3.4 of the CS8900 Data
Sheet for additional information on the op-
eration of the EEPROM.
Addr
Word
Description
00h
A110h
Sequential EEPROM, 16 bytes follow
01h
0020h
1 word into PP_020 (IO Base Addr)
02h
0210h
IO Base Address = 210h
03h
3030h
4 words beginning at PP_030
04h
8000h
Boot PROM base at C8000h
05h
000Ch
06h
C000h
Boot PROM mask of FC000h (16K)
07h
000Fh
08h
1600h
Checksum
Table 3.1. Reset Configuration Block
Содержание CRYSTAL LAN CS890
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