GT-64260A Design Guide
Doc. No. MV-S300165-00, Rev. A
CONFIDENTIAL
Copyright © 2002 Marvell
Page 144
Document Classification: Proprietary Information
May 21, 2002, Preliminary
Section 20. Reset
The GT-64260A implements three reset pins.
Note
Since the read and write pointers to the PCI interface unit FIFOs must be synchronized, it is necessary to
assert the SysRst when the Rst signal is asserted. Some of the pointers are reset with the SysRst signal
and some of them are reset with the Rst signal.
Some systems require the PCI devices to be reset, but not the GT-64260A and the CPU. For example, the CPU
gets data from the GT-64260A communication ports and routes it to other GT-64260A interfaces (PCI, MPSC,
etc.). Even if the PCI is in reset state, the system can still receive and send packets to the network. The system
must notify the CPU that the PCI interface is currently not available. It then resets the PCI interface. To complete
this reset sequence, the GT-64260A PCI reset signals must be separated from all other PCI devices and it must
not be asserted when all of the PCI devices are being reset.
The recommended sequence for this example above is as follows:
1.
In the PCI Status and Command register (Offset: 0x04 and 0x84), disable the IOEn bit [0], MasEn bit [2], by
setting these bits to ’0’.
2.
For the PCI slave, disable the same bits.
3.
In the CPU Configuration register (Offset: 0x000), disable the GT-64260A synchronization barrier capabilities
by setting ConfSBDis and IOSBDis bits [29:28] to ’1’.
4.
Reset all the PCI devices, except for the GT-64260A. No configuration cycles are allowed prior to the PCI
reset assertion.
5.
After the PCI reset de-asserts the PCI master, the PCI slave and the synchronization barrier capabilities must
be enabled.
20.1 Reset Configurations
The GT-64260A is configured at reset de-assertion via AD[31:0]. Additionally, it can be configured via Serial ROM
initilization. For more information, see the GT-64260A datasheet’s "Reset Configuration" section.
Note
There cannot be any bus holds on the AD[31:0] bus. The GT-64260A must sample the configuration
signals at a valid voltage level.