Computer Link with 3964(R) Transmission Protocol
S5-95U, Second Serial Interface
Initialization conflict
An initialization conflict occurs if a communication partner does not respond with DLE or NAK to the
send request (STX character) of the other communication partner within the specified timeout and
sends an STX character instead. This means that both communication partners want to send at the
same time. The device with low priority will then postpone its send request and responds with the
DLE character. The device with high priority sends the data as described above. After connection
cleardown, the device with low priority can make a send request.
The
”
PRI
”
(priority) parameter must be set when parameterizing the 3964(R) driver in DB1. Make
sure to assign different priorities to the devices.
Solving an initialization conflict (example):
Figure 3-14 Solving an Initialization Conflict
a a a
a a a
a a a
a a a
a a a
a a a
a a a
a a a
a a a
a a a
.
.
:
:
:
STX
DLE
1st character
STX
DLE
DLE
BCC
*
ETX
DLE
nth character
1st character
STX
Communication partner
High priority
S5-95U
3964(R) driver
Low priority
* BCC only with 3964R transmission protocol
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EWA 4NEB 812 6095-02