Basic Principles of Serial Data Transmission
2-35
Point-to-point connection CP 440 Installation and Parameter Assignment
A5E00057742-02
Receiving with the 3964(R) Procedure (Part 2)
The figure below illustrates receiving with the 3964(R) procedure.
Start T
char. delay time
3964
4
Start T
char. delay time
Send DLE
G
Note
NAK
Start T
char. delay time
Dual DLE
Note NAK
Times: T
char. delay time
= 220 ms, T
Block
= 4 s
W = transmission attempt counter
BCC only with 3964(R)
Immediate return to initial state at line break (BREAK)
Wait to
receive
characters
Invalid character
Correct
character
except
for DLE
DLE
Wait for
ETX
ETX
T > T
char. delay time
T > T
char. delay time
3964(R)
Wait for
BCC
BCC
NAK noted
Receipt completed
Send NAK
W > 5
W <= 5
Note repetition
expected, start T
BLOCK
STX
T > T
char.
delay time
BCC incorrect
Characters
except ETX, DLE
3
Wait for
STX
1
T >
T
BLOCK
G
Initialization conflict
noted, low priority
Figure 2-20
Flow Diagram of Receiving with the 3964(R) Procedure (Part 2)
Содержание SIMATIC CP 440
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