Sequential With And Without Loopback; Creating One-Dimensional Buffers - Analog Devices VisualDSP++ 5.0 Service Manual

The circular dataflow method is suitable for steady, continuous dataflow,
where the entire data fits in a 64K byte maximum contiguous block of
memory. Streaming audio data, assuming it fits within the 64 K byte
block of memory, is sometimes appropriate for the circular dataflow
method. This saves the overhead of having to create multiple buffers as is
necessary using the chained-with-loopback method. Generally, video data
is not appropriate for the circular dataflow method, since video data is fre-
quently larger than the 64K byte maximum for circular dataflow.

Sequential With and Without Loopback

The sequential dataflow method, with and without loopback, is suitable
only for devices that employ half-duplex, serial type communication
protocols. For example, the two-wire interface (TWI) device driver uses
the sequential dataflow methods to precisely schedule reads and writes in a
specific order.

Creating One-Dimensional Buffers

The
ADI_DEV_1D_BUFFER
data that a device driver processes. Applications populate the various fields
of the buffer to completely describe the data to the device driver. For
one-dimensional buffers, applications populate the following fields of the
ADI_DEV_1D_BUFFER
• – If the buffer is provided to the
Data
this field contains the starting address of the data sent out through
the device. If the buffer is provided to the
tion, this field contains the starting address of where the device
driver stores data received in from the device.
•
ElementCount
pointed to by the data pointer.
VisualDSP++ 5.0 Device Drivers and System
Services Manual for Blackfin Processors
data structure is used to describe a linear array of
structure:
– This field indicates the number of elements
Device Driver Manager
function,
adi_dev_Write()
adi_dev_Read()
func-
10-19