7.5.2 FC/SFC 218 - SER_RCV - Receive from PtP
This block receives data via the serial interface. Using the FC/SFC 218 SER_RCV after
SER_SND with the protocols USS and Modbus the acknowledgement telegram can be
read.
More information about the usage of these blocks may be found in the
manual "SPEED7 Operation List" from VIPA.
7.6 Protocols and procedures
The CPU supports the following protocols and procedures:
n
ASCII communication
n
STX/ETX
n
3964R
n
USS
n
Modbus
ASCII data communication is one of the simple forms of data exchange. Incoming char-
acters are transferred 1 to 1. At ASCII, with every cycle the read FC/SFC is used to store
the data that is in the buffer at request time in a parametrized receive data block. If a tele-
gram is spread over various cycles, the data is overwritten. There is no reception
acknowledgement. The communication procedure has to be controlled by the concerning
user application. For this you can use the FB 1 - Receive_ASCII.
More information about the usage of this block may be found in the
manual "SPEED7 Operation List" from VIPA.
STX/ETX is a simple protocol with start and end ID, where STX stands for
S
tart of
T
e
x
t
and ETX for
E
nd of
T
e
x
t.
n
Any data transferred from the periphery must be preceded by a Start followed by the
data characters and the end character. Depending of the byte width the following
ASCII characters can be transferred: 5bit: not allowed: 6bit: 20...3Fh, 7bit: 20...7Fh,
8bit: 20...FFh.
n
The effective data, which includes all the characters between Start and End are trans-
ferred to the CPU when the End has been received.
n
When data is send from the CPU to a peripheral device, any user data is handed to
the FC/SFC 217 (SER_SND) and is transferred with added Start- and End-ID to the
communication partner.
n
You may work with 1, 2 or no Start- and with 1, 2 or no End-ID.
n
If no End-ID is defined, all read characters are transferred to the CPU after a parame-
terizable character delay time (Timeout).
As Start-res. End-ID all Hex values from 01h to 1Fh are permissible. Characters above
1Fh are ignored. In the user data, characters below 20h are not allowed and may cause
errors. The number of Start- and End-IDs may be different (1 Start, 2 End res. 2 Start, 1
End or other combinations). For not used start and end characters you have to enter FFh
in the hardware configuration.
Message structure:
Overview
ASCII
STX/ETX
VIPA System 300S
+
Deployment PtP communication
Protocols and procedures
HB140 | CPU-SC | 313-5BF23 | en | 19-01
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