DHL Driver
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has been transferred to HST channel frames, the DHL device returns the
current frame to the channel’s pipe. In this situation, if the HST channel’s
frames can hold more data than the stream’s buffers, the frames always
return to the HST pipe partially full.
The maximum performance in a DHL device is obtained when you
configure the frame size of its HST channel to match the buffer size of the
stream that uses the device. The second best alternative is to configure
the stream buffer (or HST frame) size to be larger than, and a multiple of,
the size of the HST frame (or stream buffer) size for input (or output)
devices. Other configuration settings also work since DHL does not
impose restrictions on the size of the HST frames or the stream buffers,
but performance is reduced.
Constraints
❏
HST channels used by DHL devices are not available for use with
PIP APIs.
❏
Multiple streams cannot use the same DHL device. If more than one
stream attempts to use the same DHL device, a SYS_EBUSY error
is reported in the system LOG during startup when the BIOS_start
routing calls the DHL_open function for the device.
DHL Driver Properties
The following global property can be set for the DHL - Host Link Driver on
the DHL Properties dialog in the DSP/BIOS Configuration Tool or in a
Tconf script:
❏
Object memory
. Enter the memory segment from which to allocate
DHL objects. Note that this does not affect the memory segments
from where the underlying HST object or its frames are allocated.
The memory segment for HST objects and their frames can be set
using HST Manager Properties and HST Object Properties.
Tconf Name: OBJMEMSEG
Type: Reference
Example:
DHL.OBJMEMSEG = prog.get("myMEM");
DHL Object Properties
The following properties can be set for a DHL device using the DHL
Object Properties dialog in the DSP/BIOS Configuration Tool or in a
Tconf script. To create a DHL device object in a configuration script, use
the following syntax:
var myDhl = bios.DHL.create("myDhl");
The Tconf examples assume the myDhl object has been created as
shown.
❏
comment
. Type a comment to identify this object.
Tconf Name: comment
Type: String
Example:
myDhl.comment = "DHL device";