Avago Technologies LSI53C1020 - Manual (Page 54)

2-28 Functional Description
Version 2.4 Copyright © 2001–2004 by LSI Logic Corporation. All rights reserved.
2.7 Zero Channel RAID
Zero channel RAID (ZCR) capabilities enable the LSI53C1020 to
respond to accesses from a PCI RAID controller card or chip that is able
to generate ZCR cycles. The LSI53C1020 ZCR functionality is controlled
through the ZCR_EN/ and the IOPD_GNT signals. Both of these signals
have internal pull-ups and are active LOW.
The ZCR_EN/ signal enables ZCR support on the LSI53C1020. Pulling
ZCR_EN/ HIGH disables ZCR support on the LSI53C1020 and causes
the LSI53C1020 to behave as a normal PCI-X to Ultra320 SCSI
controller. When ZCR is disabled, the IOPD_GNT signal has no effect on
the LSI53C1020 operation.
Pulling ZCR_EN/ LOW enables ZCR operation. When ZCR is enabled,
the LSI53C1020 responds to PCI configuration cycles when the
IOPD_GNT and IDSEL signal are asserted. Connect the IOPD_GNT pin
on the LSI53C1020 to the PCI GNT/ signal of the external I/O processor.
This allows the I/O processor to perform PCI configuration cycles to the
LSI53C1020 when the I/O processor is granted the PCI bus. This
configuration also prevents the system processor from accessing the
LSI53C1020 PCI configuration registers.
Figure 2.6 illustrates how to connect the LSI53C1020 to enable ZCR.
This figure also contains information for connecting the
LSI53C1000R-based designs to a ZCR design and migrating from
LSI53C1000R-based designs to LSI53C1020-based designs. Notice that
the LSI53C1020 does not require the 2:1 mux.