Siemens SINAUT ST7 System Manual page 134

Glossary
Image memory / send buffer principle
● Image memory principle
A fixed position is reserved in the image memory for each data frame transferred to the
TIM for transmission. Each newly transferred frame always overwrites the old frame in the
image memory.
If a send frame is entered using the image memory principle, only a reference to the
location of the frame in the frame image memory is entered. If the TIM has not yet been
able to transmit the frame when the same frame is transferred to it again, the frame is not
entered in the send buffer a second time, but rather the image is simply updated.
At the time of transmission, the frame is sent with its up-to-date content from the image
memory. Only then can the frame be entered in the send buffer again.
Transmission using the image memory principle achieves the following:
– There is less load on transmission link, fewer frames are transmitted.
– There is less load on the send buffer of the TIM; an image memory frame is entered a
● Send buffer principle
If a data frame is transmitted using the send buffer principle, it is entered completely in
the send buffer each time it is transferred to the TIM. If such a frame cannot or should not
be transmitted immediately, it may therefore exist more than once in the send buffer.
When it is sent, the frame is taken completely from the send buffer and transmitted.
Inter-station communication
Communication between two stations, which is mediated by a Telecontrol master station.
In dial-up networks, a direct connection between the two stations is established.
See also "Direct communication".
IRC
Industrial Remote Communication
SIMATIC NET product group for Telecontrol
ISDN
Integrated Services Digital Network
Standard for a digital transmission network for telephone, telefax, telex, teletext and datex-
J/L/P services. The data of various services can be transferred simultaneously. Telephone
connections normally operate at transmission speeds of 56 to 64 Kbps.
LAN
Local Area Network
Local network, usually "Industrial Ethernet".
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maximum of once in the send buffer.
SINAUT ST7 - Volume 1
System Manual, 11/2018, C79000-G8976-C178-12