
SYM53C895 Interfaces
2-15
The format of the serial EEPROM data is dened in
Table 2.3. If the
EEPROM is not present, or the checksum fails, the Subsystem ID and
Subsystem Vendor ID registers read back all zeroes. At power-up or hard
reset, only ve bytes are loaded into the chip from locations 0xFB
through 0xFF.
2.6.2.4 Mode D: 4.7 K
Pull-up on MAD6, and 4.7 K Pull-down on MAD7
This is a reserved mode and should not be used.
2.6.3 SCSI Bus Interface
The SYM53C895 performs SE and LVD transfers, and supports
traditional (high-power) differential operation when the chip is connected
to external high-power differential transceivers.
To support LVD SCSI, all SCSI data and control signals have a positive
and a negative signal line, as in high voltage differential. In SE and HVD
operation, the negative signals perform the SCSI data and control
Table 2.3
Mode C Serial EEPROM Data Format
Byte
Description
0x00–0xFA
Contains user data.
0xFB
Subsystem Vendor ID, LSB. This byte is loaded into the least
signicant byte of the Subsystem Vendor ID register in PCI
conguration space at chip power-up or hard reset.
0xFC
Subsystem Vendor ID, MSB. This byte is loaded into the most
signicant byte of the Subsystem Vendor ID register in PCI
conguration space at chip power-up or hard reset.
0xFD
Subsystem ID, LSB. This byte is loaded into the least
signicant byte of the Subsystem ID register in PCI
conguration space at chip power-up or hard reset.
0xFE
Subsystem ID, MSB. This byte is loaded into the most
signicant byte of the Subsystem ID register in PCI
conguration space at chip power-up or hard reset.
0xFF
Checksum. This 8-bit checksum is formed by adding, bytewise,
each byte contained in locations 0xFB–0xFE to the seed value
0x55, and then taking the 2’s compliment of the result.
0x100–EOM
Contains user data.