Siemens SIMATIC TIWAY 1 - Manual (Page 40)

OPERATION AND APPLICATION
UNILINK HOST ADAPTER 2–30
USER MANUAL
2.10 EXTENDED NETWORK OPERATIONS
The Extended HIU (EHIU) commands provide several performance
improvement benefits through macros and bandwidth adjustments.
2.10.1 What Are Macros?
Normally, when the host computer issues a network request to connect,
disconnect, and send data to and from secondary devices, it must wait for the
response to be returned. Macros are network requests that are stored and
scheduled for independent processing by the HIU function. The HIU function
will issue the network request at the proper time and store the response. This
frees the host computer to issue other commands and retrieve request
responses without the burden of real-time host computer control. The HIU
function is free to schedule macro transmissions and collect responses, so that
new macro requests can be issued to the NM function while waiting for older
ones to complete processing in the secondary devices. This keeps the network
efficient and increases data throughput.
2.10.1.1 Configuration Modes Supporting Macros
Table 2–1 Configuration Modes Supporting Macros
Macros supported? No
MHIU
EHA
No
HIU
EHA
Yes
MHIU
Yes
HIU
No
NM
No
NM
SA
The UNILINK Host Adapter must be configured as either a Master Host
Interface Unit or a Host Interface Unit to use the macro feature. These two
operating modes accept the extended host commands for defining macros and
collecting macro responses. Macros are not supported in the Emulate Host
Adapter modes.