Device Interface Functional Overview
8-bit Device
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 53
The GT-64260A device controller supports 8-, 16-, or 32-bit wide devices. The device width is specified in the
Device Bank Parameters register’s bits
DevWidth
[21:20], at offsets 0x45c, 0x460, 0x464, 0x468, and 0x46c. The
boot device width is sampled at reset on
AD
bits[15:14] pins and sets the corresponding bits in the Boot Device
Parameters register, at offset 0x46c. For more information on the reset settings, see
6.2
8-bit Device
The GT-64260A device controller supports 8-bit wide devices connected on the AD[7:0] bus. The device controller
support up to 8 byte bursts to/from 8-bit devices. The burst address is supported by a dedicated three bit BAdr
[2:0] bus that must be connected directly to the device address bus.
shows the connection of an 8-bit wide device to the GT-64260A. For more information on the 8-bit
device connection, see the GT-64260A datasheet’s "Interfacing With 8/16/32-Bit Devices" section.
Note
The device controller does not support bursts longer than 8B. Any attempt to support longer bursts causes
the GT-64260A to assert an interrupt. For more information on the interrupt assertion, see
"Interrupt Controller Functional Overview", on page 82
. The following restrictions are also implied.
–
The CPU must configure the memory space of an 8-bit device as uncacheable space.
–
Since the IDMA engines do not support a data transfer limit smaller than 8B, the only DTL allowed from
the IDMA engine to an 8-bit device is 8B.
–
When using MPC745x CPU, the boot device must be 32-bit wide. For more information, see
3.5.1, "MPC745x Burst to Boot Address", on page 21
–
It is only possible to read 8-bit devices from a PCI non-prefetchable region.