1. Functional Overview
27
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
1.5
I
2
C / EEPROM
1.5.1
EEPROM
PowerSpan II registers can be programmed by data in an EEPROM at system reset. This enables board
designers to set unique identifiers for their cards on the PCI bus at reset, and set various image
parameters and addresses. Configuring PowerSpan II with the EEPROM allows PowerSpan II to
boot-up as a Plug and Play compatible device. PowerSpan II supports reads from, and writes to, the
EEPROM.
1.5.2
I
2
C
PowerSpan II has a master only I
2
C bus compatible interface which supports up to eight I
2
C slave
devices. This interface is used by PowerSpan II for the initialization of registers and for reading and
writing PCI Vital Product Data (VPD).
PowerSpan II also provides a mechanism to perform master read and write operations to EEPROMs or
other I
2
C compatible slave devices.
1.6
Concurrent Reads
PowerSpan II’s Switched PCI architecture enables concurrent reads through a single channel. This
ability greatly reduces read latency, which is often the limiting factor in PCI performance.
1.6.1
PowerSpan II’s Concurrent Read Solution
With PowerSpan II’s concurrent reads, read requests are accepted even while the current read is in
progress.
illustrates the concurrent read process with the PowerSpan II.