Sundance SMT6035 v.2.2 - Manual (Page 24)

Version 2.2 Page 24 of 39 SMT6035 User Manual
15.2.3 DSP reading from the host
Before the DSP reads data from the host, it writes a control word to the
host indicating it. The host reads this command from the DSP, places
the data in the appropriate memory and replies to the DSP when it has
done so.
Host
DSP Section
Waits for control word Sends control word to host
Receives control word Waits for host’s reply Sect 15.6.16
Prepares shared memory
(PCI or SRAM)
Sends reply to DSP Sect 15.6.17
Read operation complete
15.3 SRAM arguments
The SRAM acts as a shared memory buffer between the DSP and the host. For
each channel an area of the SRAM is reserved for communicating data. This
area is called the argument space, and is limited to 64 Kbytes per channel.
The SMT6035 provides utility functions that allow the host to access the
parameter area for each channel. Similarly, on the DSP side, 3L Diamond
© has
utility functions with which you can access the SRAM argument areas.
15.4 PCI memory access
In case of PCI memory access, the DSP can use the host PCI memory space
via the PCI bridge chip. The host memory has to be locked before the DSP will
be able to safely gain access this memory. The host operating system must not
page to disk any locked memory, and must ensure that the memory remains at
a fixed location.
With the SMT6035, the PCI memory will be automatically locked when you
define a virtual channel. During this stage, a memory descriptor list (MDL) for
the locked down memory will be copied into the SRAM for later use by the DSP.
It is possible to lock a contiguous memory region. However, this memory region
has to be provided from the non-paged system memory pool, and this is a
scarce system resource. It is not advisable to lock large amounts of contiguous
memory on the host, as this will seriously degrade system performance and
may make the host system unstable.
Using a high-speed channel (HSC), it is possible to transfer blocks of up to
16MB of data at a time between the host and the root DSP. Typical transfer
User Manual - Version 2.2, 04/01/07; © Sundance Italia S.R.L.