Siemens SIMATIC TIWAY 1 - Manual (Page 54)

OPERATION AND APPLICATION
UNILINK HOST ADAPTER 2–44
USER MANUAL
UNILINK Host Adapter
Macro Response Buffer #A
Macro Response Buffer #B
Secondary
#1
Secondary
#2
Data Packet
Data Packet
Figure 2–19 Link Macro Store and Forward Operation
Both macros must be disabled before the LINK MACRO command will be
accepted. The trigger macro must be a valid Primitive 20 or A0 to read data from
the secondary device. The action macro must be a valid Primitive 30 or B0 to
write the data read to the other secondary. All of the define macro options on
each macro command buffer are valid until the link is established. When the
link is established, the action macro will be considered non-repetitive. When the
link is terminated the original conditions will be valid again.
The adapter will check the validity of the host supplied Primitives before
linking them. The Primitives must use the same TT type, but may use different
starting addresses (AAAA field of the Primitive). You must insure that the
number of TT types (NNNN field of Primitive) and the starting addresses are
valid for both secondaries involved.
Once the link is established, just enable the trigger macro to begin the process.
The trigger macro behaves much like a non-linked macro, except that it is
disabled while the action macro executes. Each time the trigger macro
completes a read, the trigger macro is disabled, its data moved into the action
macro buffer to create a valid write Primitive and the action macro is enabled. If
the trigger macro receives an error from the secondary, the action macro is not
enabled and the exception flag is set disabling the trigger macro.