GT-64260A Design Guide
Doc. No. MV-S300165-00, Rev. A
CONFIDENTIAL
Copyright © 2002 Marvell
Page 50
Document Classification: Proprietary Information
May 21, 2002, Preliminary
If the REQ64* pin is sampled high at PRst* de-assertion, the PCI interface is configured to 32-bit mode. Since the
GT-64260A drives the dedicated 64-bit mode pins (e.g., AD[63:32], CBE[7:4], REQ64*, ACK64* and PAR64*) in
32-bit mode, these bits must not be connected to any other device that might be driving them (e.g., two GT-
64260A connected as 64-bit PCI but configured in a 32-bit mode).
5.5
Cache Coherency
The GT-64260A supports cache coherency between PCI and SDRAM. Each PCI transaction to a cache coherent
region generates a snoop transaction on the CPU bus.
Note
A read transaction from the WT cache region does not generate a snoop transaction on the CPU bus.
There are up to four configurational address ranges in which cache coherency is maintained. The PCI Snoop
Base and Top Address registers define the cache coherent address windows. See
.
5.6
Message Signaled Interrupt (MSI)
The optional Message Signaled Interrupt (MSI) feature enables a device to request service by writing a system
specified message to a system specified address. Devices that do not support interrupt pins may implement mes-
sages to increase performance without adding additional pins.
The MSI is defined in the PCI specification. For more information, see the PCI specification, Section 6.8 "Message
Signaled Interrupts" in the PCI specification and the GT-64260A datasheet’s "Message Signaled Interrupts" sec-
tion.
Note
In the following initialization procedure, the first offset number is for PCI_0, and the second is for PCI_1.
The MSI initialization procedure is as follows:
1.
Set the PCI Mode register’s
MSI
bit [10] to ’1’, at offsets 0xD00 and 0xD80.
2.
Set the PCI MSI Message Control register’s
MSIEn
bit [16] to ’1’, at offsets 0x50 and 0xd0.
3.
If DAC (64 bit addressing mode) is needed, the PCI MSI Message Control register’s
Addr64
bit [23] must be
set to ’1’. Also, the PCI Command register’s
MDACEn
bit [17] must be set to ’1’, at offsets 0xc00 and 0xc80.
4.
Set the message address in the PCI MSI Message Address registers, at offsets 0x54 and 0xd4. If DAC is
needed, set the PCI MSI Message Upper Address registers, at offsets 0x58 and 0xd8. The GT-64260A ini-
tiates a write transaction to this address as soon as an interrupt is pending.
5.
Set the control data in the PCI MSI Data Control register (at offset 0x5c and 0xdc). This register specifies the
data for the write transaction above.
6.
Unmask the interrupt, so that the MSI signals in the PCI Interrupt Mask (Low) or PCI Interrupt Mask (high)
registers, at offsets 0xc24, 0xca4, 0xc64, and 0xce4.
7.
Unmask the interrupt, so that the MSI must signal in the interrupting unit. For more information on the inter-
rupt controller, see
Section 11. "Interrupt Controller Functional Overview" on page 82
.