58
AN83REV1
CS8900 Technical Reference Manual
1.) The base of the data structure must be
marked by a header consisting of the 8-byte
ASCII text string “$CS8900$”.
2.) The header must be located on a 512-
byte boundary in the BIOS space between
C0000h and FFC00h.
3.) The data structure must employ the
same format as defined for EEPROM in
Table 3.2.
An additional design consideration when
storing the Driver Configuration Block in
BIOS space concerns the inability to over-
ride the CS8900’s default configuration
after reset. If an EEPROM is not con-
nected to the CS8900, it will always come
out of reset using its default configuration.
Therefore, when using BIOS space to store
configuration information, IO addresses of
300h - 310h must be dedicated to the
CS8900.
The CS8900’s configuration can be
changed from its default values through
software control after reset. However, it
will always revert to its default configura-
tion after each reset (including software
resets). Refer to Table 3.3 of the CS8900
Data Sheet for default configuration defi-
nitions.
3.2.2 Driver Interface with BIOS-Based
Configuration
During initialization, Crystal-provided
drivers test for the presence of an
EEPROM. If an EEPROM is not detected,
the drivers scan the BIOS for the header
indicating the start of a Driver Configura-
tion Block. Before using the data in the
Driver Configuration Block, the drivers
verify the data in the block is valid using a
checksum.
The checksum stored at the end of the
block is the 2’s complement of the 16-bit
sum of all the words in the Driver Configu-
ration Block, excluding the 8 bytes of
header. (The drivers access the Configura-
tion Block in BIOS space as 16-bit words.)
Any carry out of the 16th bit is ignored.
Since this checksum value is calculated as
the 2’s complement of the sum of all the
preceding words in the block, a total of 0
should result when the checksum value is
added to the sum of the previous words.
Table 3.3 shows the correct format for a
data structure storing the Driver Configu-
ration Block in BIOS space.
Содержание CRYSTAL LAN CS890
Страница 26: ...26 AN83REV1 CS8900 Technical Reference Manual Figure 2 2 9 CRD8900 Top Side Routing ...
Страница 27: ...AN83REV1 27 CS8900 Technical Reference Manual Figure 2 2 10 CRD8900 Bottom Side Routing ...
Страница 36: ...36 AN83REV1 CS8900 Technical Reference Manual Figure 2 4 2 Ground connection Top layer of two layer Combo Card ...
Страница 40: ...40 AN83REV1 CS8900 Technical Reference Manual Figure 2 4 6 Component top side of four layer board ...
Страница 41: ...AN83REV1 41 CS8900 Technical Reference Manual Figure 2 4 7 5V Plane of four layer board ...
Страница 42: ...42 AN83REV1 CS8900 Technical Reference Manual Figure 2 4 8 Ground Plane of four layer board ...
Страница 43: ...AN83REV1 43 CS8900 Technical Reference Manual Figure 2 4 9 Solder side bottom of four layer board ...