2. PCI Interface
60
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
2.5
Vital Product Data
Vital Product Data (VPD) is information which uniquely defines items of a system. These items
include the hardware, software and microcode elements of a system. VPD also provides a mechanism
for storing information, such as performance data on a device. VPD resides in a local storage device.
PowerSpan II supports VPD through the I
2
C Interface to serial EEPROM. The Vital Product Data
Extended Capabilities Pointer and supporting registers reside in the configuration space of the
PowerSpan II Primary PCI Interface. The VPD feature requires the VPD_EN bit, in the
Control and Status Register” on page 318
, to be set and an available external EEPROM.
2.5.1
VPD Access
VPD accesses through PowerSpan II default to the I
2
C serial EEPROM device zero (VPD EEPROM
Chip Select (VPD_CS) = 0b000 in the
“Miscellaneous Control and Status Register” on page 318
). This
is also used for EEPROM loading of the registers after reset. Since the lower bytes in the EEPROM
contain data for setting up PowerSpan II before software initialization, the lower portion of the
EEPROM
(
the first 64 bytes)
are not visible through the VPD registers. The upper 192 bytes of the 256
byte EEPROM are visible through the VPD registers. Of these bytes, the first 64 bytes are VPD-Read
Only and the remaining 128 bytes are VPD-Read/Write. When VPD_CS = 0b000, VPD addresses are
translated upward by 64 bytes before being presented to the EEPROM.
PowerSpan II can be programmed with an alternate chip select for VPD access if more than the 192
accessible bytes is required. Programming of the I
2
C chip select is done in the PowerSpan II
“Miscellaneous Control and Status Register” on page 318
. If an alternate I
2
C chip select is used then
the first 64 bytes of the VPD EEPROM is designated as VPD-Read Only and the upper 192 bytes are
designated as VPD-Read/Write.
The VPD access to the EEPROM is similar to the EEPROM access implemented in PowerSpan II
through the I2C_CSR register, except that it uses the
“PCI-1 Vital Product Data Capability Register”
“PCI-1 Vital Product Data Register” on page 267
. Since they both access the same
resource, a PowerSpan II semaphore register SEMAx must be used to acquire exclusive access of the
I
2
C Interface before software initiates VPD accesses.
2.5.2
Reading VPD Data
PowerSpan II implements 8-bits of address for accessing the EEPROM up to a maximum of 256 bytes.
The VPD address must be DWORD-aligned. A single read access reads four consecutive bytes starting
from the VPD address from the EEPROM. If I
2
C chip select zero is used for VPD, then 192 bytes
(address 0x00-BF) of VPD are accessible through the VPD read. Using another I
2
C chip select, the
VPD Read can access the entire 256-byte EEPROM address range.