&KDSWHU
7+(25< 2) 23(5$7,21
90( *DWHZD\
&KDSWHU
7+(25<2)23(5$7,21
The L5211 is essentially a dual ported, random access memory (RAM) which is
installed directly into the VME Bus and is interconnected to the LINK network. 32K
of RAM is available, much of which may be used by the VME programmer for
general purpose data storage. Future versions of the device may use more memory for
the intended functionality, that of passing data back and forth between the VME bus
and the LINK network.
0(025<
Memory is referenced from a "base", or starting address; that is, the lowest address
into which data may be stored. For the purposes of this discussion, the base address
will be referred to as $000 ($ specifies hexadecimal) . Refer to the installation
instruction section of this manual for details on how to set the base address. The
memory is configured in byte format.
6+$5(' 0(025<
"Shared memory" is that portion of the 32K RAM that is accessed by both the VME
and the LINK network for purposes of communication. Shared memory presently
resides between $000 and $29F, and is broken up into six specific regions. These
regions, defined in Table 1, facilitate the transfer of bits, bytes, and words, from each
device to the other. Further, Flags are used to notify the receiving device that a
particular value has been changed.
'DWD $GGUHVV
)ODJ %\WHV
7\SH
'LUHFWLRQ
%
%LW
90( WR /LQN
& %
)
%\WH
90( WR /LQN
& %
%
:RUG
90( WR /LQN
&
&
%LW
/LQN WR 90(
%\WH
/LQN WR 90(
)
:RUG
/LQN WR 90(
7DEOH 0HPRU\ 5HJLRQ 'HILQLWLRQ
)/$* %<7(6
The Flag bytes provide an efficient means of controlling the flow of data between the
two mediums. When data is written from one device to the other, the sending device
must set the appropriate bit in the Flag byte to notify the receiver of the change in
data. Therefore, simply scanning the flags allows the receiver a convenient means of
determining if data has been modified. The use of this feature is optional on data
