Siemens S7-1200 - Page 692

Communication processor and Modbus TCP
12.3 Point-to-point (PtP) communication
S7-1200 Programmable controller
692 System Manual, 03/2014, A5E02486680-AG
End conditions for the RCV_PTP instruction
The end of a message is determined by the specification of end conditions. The end of a
message is determined by the first occurrence of one or more configured end conditions.
The section "Message end conditions" in the topic "Configuring receive parameters
(Page 676)" describes the end conditions that you can configure in the RCV_CFG
instruction.
You can configure the end conditions in either the properties of the communication interface
in the device configuration, or from the RCV_CFG instruction. Whenever the CPU transitions
from STOP to RUN, the receive parameters (both start and end conditions) return to the
device configuration settings. If the STEP 7 user program executes RCV_CFG, then the
settings are changed to the RCV_CFG conditions.
Parameter CONDITIONS data type structure part 2 (end conditions)
Table 12- 17 CONDITIONS structure for END conditions
Parameter
Parameter type
Data type
Description
ENDCOND IN UInt
0
This parameter specifies message end condition:
• 01H - Response time
• 02H - Message time
• 04H - Inter-character gap
• 08H - Maximum length
• 10H - N + LEN + M
• 20H - Sequence
MAXLEN IN UInt
1
Maximum message length: Only used when the
maximum length end condition is selected. 1 to 1024
bytes
N IN UInt
0
Byte position within the message of the length field. Only
used with the N + LEN + M end condition. 1 to 1022
bytes
LENGTHSIZE IN UInt
0
Size of the length field (1, 2, or 4 bytes). Only used with
the N + LEN + M end condition.
LENGTHM IN UInt
0
Specify the number of characters following the length
field that are not included in the value of the length field.
This is only used with the N + LEN + M end condition. 0
to 255 bytes
RCVTIME IN UInt
200
Specify how long to wait for the first character to be
received. The rece
ive operation will be terminated with an
error if a character is not successfully received within the
specified time. This is only used with the response time
condition. (0 to 65535 bit times with an 8 second
maximum)
This parameter is not a message end condition since
evaluation terminates when the first character of a
response is received. It is an end condition only in the
sense that it terminates a receiver operation because no
response is received when a response is expected. You
must select a separate end condition.