Re: DMA across PCI

["Weng Tianxiang" <wtx@umem.com>]

Hi Daniel,

In PCI world, DMA = MASTER +  a set of registers in the Board. No PCI references mention it.

 

PCI is a highway, DMA is a public bus company that runs on the highway.

 

A set of registers in the Board:

1. PCI system memory address;

2. Local address;

3. Byte count to transfer;

4. Direction bit: PCI --> Board or Board --> PCI;

5. Go bit: if it is set, Master starts doing the designated job;

6. Status bits;

7. Other Board-dependent feathers;

 

To make these registers accessable to system software, one should allocate space for the registers through BARx in PCI configuration space.

 

After above hardware design, software can get the registers' memory address and size, then write commands to them, the final word to write is Go bit. After Go bit is set, Master will start designated operation and return status or interrupt if it finishes the job or any errors happen.

 

Weng Tianxiang
Micro Memory Inc.
9540 Vassar Av.
Chatsworth, CA 91311
Phone: 818-998-0070, Fax: 818-998-4459

 

----- Original Message -----

From: Daniel DeConinck

To: pci-sig@znyx.com

Sent: Saturday, October 14, 2000 8:48 AM

Subject: DMA across PCI

Hello,

 

I looked in the index of the PCI spec 2.1 and the index of "PCI System Architecture", by Mindshare, Inc. Niether had a reference to DMA.

 

I am guessing that there is no such thing as DMA in the PCI world. Is that the case ?

 

I further guess that the closest thing to DMA is a Master read or a Master write cylce.

 

Please enlighten me.

 

Sincerely
Daniel DeConinck
High Res Technologies, Inc.