IDMA Unit Functional Overview
Copyright © 2002 Marvell
CONFIDENTIAL
Doc. No. MV-S300165-00, Rev. A
May 21, 2002, Preliminary
Document Classification: Proprietary Information
Page 79
Section 10. IDMA Unit Functional Overview
The GT-64260A IDMA controller transfers blocks of data independent of the local processor or PCI hosts. Data
movement can occur from any interface to any interface.
The GT-64260A implements eight IDMA channels. Each IDMA engine can move data between any source and
destination, such as the SDRAM, Device, PCI_0, PCI_1, or CPU bus.
The IDMA controller can be programmed to move up to 16 MB of data per transaction. The burst length of each
transfer of IDMA can be set from 8 bytes to 128 bytes. Accesses can be non-aligned both in the source and the
destination.
The IDMA controller clock source is the TClk input, the same clock used for the SDRAM interface. For more infor-
mation about the GT-64260A clocking, see
Section 19. "Clocks" on page 143
The DMA engine implements two independent machines. The read machine performs reads from the source
address and pushes the data into the buffer. The write machine pulls data out of the buffer and writes it to the des-
tination address. With this implementation, the buffer can be filled with multiple reads before there is a write. When
the read and write accesses are to/from different interfaces (i.e., read from SDRAM and write to PCI), the
accesses can be executed in parallel.
Some additional features of the GT-64260A IDMA unit are:
•
Eight DMA channels (7:0).
•
All channels accessible by processor core and remote PCI masters.
•
Misalign transfer capability.
•
Chain mode.
•
Direct mode (non-chain mode).
•
The CPU, external request or timer/counter, can initiate DMAs transfers.
•
Interrupt on completed segment, chain, and error conditions.
•
DMA transfer to all interfaces.
•
IDMA unit contains two 2 KB buffers.
•
Increment or hold of source and destination addresses.
•
Source/Destination/Descriptor address override capability.
•
Support byte/word-swapping to/from PCI.
•
Support cache coherency between SDRAM and CPU.
shows a general flow diagram for the operation of the DMA controller.
For more information, see the GT-64260A datasheet’s "IDMA Controller" section.