Siemens SIMATIC CP 340 - Page 36

Basic Principles of Serial Data Transmission
2.4 Data Transmission with the 3964(R) Procedure
PtP coupling and configuration of CP 340
36 Manual, 04/2011, A5E00369892-03
Sending with the 3964(R) procedure
The figure below illustrates sending with the 3964(R) procedure.
No
Yes
No
QVZ
expired ?
ja
Character
received ?
Yes
Yes
Yes
Yes
With N A K ?
Yes
Intercom ?
ja
Yes
Yes
Yes
No
No
Yes
No
No
Send N A K
No
No
faulty, n ot DLE or
STX
No
A > A max ?
W > W max ?
No
S end request
Sending with pro ced u re 3964(R)
Send S T X
Send N A K
Add Q V Z
Character
received ?
Send character with
DLE doubling
Own priority high ?
Initialization conflict,
own priority low
QVZ
expired ?
More characters
to send ?
Send D LE ETX
Send B C C
Add Q V Z
With B C C
3964(R) ?
Faulty, not D L E
G 1
W = 1
A = 1
DLE
Z
STX
A + 1
W + 1
G
Z
DLE
G
4
5
6
Figure 2-7 Flow diagram of sending with the 3964(R) procedure