Siemens SIMATIC RF200 Руководство по эксплуатации - Страница 6
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Introduction
1.1 Properties of the protocol
1.1
Properties of the protocol
This protocol represents a simple communications procedure for a point-to-point connection.
The communications parameters of the serial interface are set as follows in the factory:
● Data frame with 8 data bits
● 1 stop bit
● Odd parity
● Transmission speed: 19.2 kBd
This value cannot be changed in RF200 readers.
1)
Full duplex data transfer is possible. Since no handshake is defined, both stations can send
at the same time.
The net data is transferred with the ASCII characters '0' to '9' and 'A' to 'F'. Other characters
are not permitted. For the frame, two uniquely recognizable control characters are used,
"STX [02]" for the start of the frame and "ETX [03]" for the end of the frame.
With the ASCII protocol, a third optional control character "LF [0A] = new line" (before ETX)
is possible. The reader understands this control character, configuration on the reader is
unnecessary. A frame is uniquely identified by the control characters for the start and end,
the procedure has no other reliability mechanisms or length information. The amount of data
to be transferred is restricted by the monitoring time and by the length byte in the frame.
Receipt of the frame is monitored with a monitoring time of 300 ms. If the host does not
manage to send the next character to the reader within this time until "ETX" is reached, the
frame is ignored.
Note
Restrictions resulting from the ASCII protocol
The ASCII protocol has no data consistency mechanisms. You should take this into account
in your application (e.g. checksum).
The ASCII protocol has no line monitoring mechanisms. Execute the "SLG-STATUS"
command (mode 0) at regular intervals, to ensure that the reader is reachable.
Table 1- 1
STX
0x02
Table 1- 2
ASCII
value
Hex
value
6
1)
1)
Structure of a LAUF protocol frame
Net data
ASCII values (two bytes for 1
net byte)
ASCII table with the corresponding hexadecimal values
'0'
'1'
'2'
'3'
'4'
30
31
32
33
34
{optional: LF}
{0x0A}
'5'
'6'
'7'
'8'
'9'
35
36
37
38
39
Operating Manual, 11/2016, C79000-G8976-C329-04
ETX
0x03
'A'
'B'
'C'
'D'
'E'
41
42
43
44
45
ASCII protocol for RF200
'F'
46