Black Box GEH-6510 - Manual (Page 75)

72 •••• Chapter Six - Advanced Options DDE Server User’s Guide
read. This is useful for registers with settings of a more permanent nature, which need
to be read but are unlikely to change.
Invalid Register Blocks
A register block consists of a contiguous piece of a device’s memory that contains
many points of data. Within this block, however, some addresses may be unused by
the device. We can make the PMCS DDE Server aware of these unused or
extraneous addresses by specifying them as invalid register blocks. (The Server’s
register maps for supported devices have already been optimized; only generic
devices’ invalid register blocks must be entered manually.)
An invalid register block is a list of registers within a register group that should not
be polled for data by the Server, perhaps because they are unused by the device itself
or simply because they are not desired.
Invalid register blocks allow the Server to focus its attention on only those registers
of interest; by not asking the Server to poll addresses that contain no data of interest,
we can improve the Server’s potential performance. Also, some devices, if asked for
a valid register block that happens to contain invalid registers within it, will return a
message that the entire block is invalid. Thus, it can be of vital importance to identify
any invalid blocks to the Server.