VIPA 313-6CF03, Руководство пользователя, Страница: 126 / 152

Chapter 6 Deployment PtP communication
Manual VIPA System 300S SPEED7
6-4 HB140E - CPU SC - RE_313-6CF03 - Rev. 07/45
The 3964R procedure controls the data transfer of a point-to-point link
between the CPU and a communication partner. The procedure adds
control characters to the message data during data transfer. These control
characters may be used by the communication partner to verify the
complete and error free receipt.
The procedure employs the following control characters:
•
STX
S
tart of
T
e
x
t
•
DLE
D
ata
L
ink
E
scape
•
ETX
E
nd of
T
e
x
t
•
BCC
B
lock
C
heck
C
haracter
•
NAK
N
egative
A
c
k
nowledge
STX
DLE
Message-data
DLE
ETX
BCC
Monitor delayed acknowledgment
DLE
Monitor delayed acknowledgment
Active partner Passive partner
You may transfer a maximum of 255Byte per message.
Note!
When a DLE is transferred as part of the information it is repeated to
distinguish between data characters and DLE control characters that are
used to establish and to terminate the connection (DLE duplication). The
DLE duplication is reversed in the receiving station.
The 3964R procedure requires that a lower priority is assigned to the
communication partner. When communication partners issue simultaneous
send commands, the station with the lower priority will delay its send
command.
3964R
Procedure