dual-port RAM, memory allocation/mapping

NTDEV
1

Hi,

I have a device connected to the PC via dual-port RAM. 4 bytes are mapped
for use in my driver:

devExt->DualRam = MmMapIoSpace(physAddr_dual,4,MmNonCached);

Is this enough? What else is needed for using the dual-port RAM? ( I want
only read the dual-port RAM in my driver, the device only writes it. No
synchronistation is needed.)
If my driver is running then my device is able to write only the first two
bytes. Why?

Thanks in advance,

Ferenc

2

Very strange. Can you look in the debugger on what values are read
from this memory?

Max

----- Original Message -----
From: “Ferenc Deák”
To: “NT Developers Interest List”
Sent: Tuesday, March 25, 2003 4:35 PM
Subject: [ntdev] dual-port RAM, memory allocation/mapping

> Hi,
>
> I have a device connected to the PC via dual-port RAM. 4 bytes are
mapped
> for use in my driver:
>
> devExt->DualRam = MmMapIoSpace(physAddr_dual,4,MmNonCached);
>
> Is this enough? What else is needed for using the dual-port RAM? ( I
want
> only read the dual-port RAM in my driver, the device only writes it.
No
> synchronistation is needed.)
> If my driver is running then my device is able to write only the
first two
> bytes. Why?
>
>
>
> Thanks in advance,
>
> Ferenc
>
>
>
> —
> You are currently subscribed to ntdev as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to
xxxxx@lists.osr.com
>

3

> Very strange. Can you look in the debugger on what values are read

from this memory?

The first three bytes:

FF FF FF

The fourth byte is unused. The first two can be changed by the device. The
third one is set to FF by the device before starting Windows.

Thanks,

Ferenc