Rs 485 Communication Description; Transmission Channel Characteristics; Message Structure - Varian Turbo-V70 Bedienungshandbuch

RS 485 Communication Description

Communication RS 485 serial port connections

Transmission channel characteristics

levels: RS485
baud rate: 9600/4800/2400/1200/600
programmable
character lenght: 8 bits
parity: none
stop bit: 1 bit
protocoll: master (PC) / slave (converter)
max. devices: 32

Message structure

(request and answer have the same format)
The master system (PC) starts every session sending
the following message to the slave units connected:
<STX> + <ADDR> + <WINDOW> +
<COMMAND> + <DATA> + <ETX> +
<CRC>
where :
<STX>= 0x02
<ADDR> = 0x80 (for RS 232 and
RS 422 only)
<ADDR> = 0x80 + device number (0...31)
0xFF: brodcasting command
(recognized by all the devices, it
doesn't implicate any answer)
(for RS 485 only)
<WINDOWS>= ' 000 '...' 999' window number
the meaning of the window
depends to the device type
<COMMAND>= 0x30: window value reading
0x31: window writing
<DATA> = alphanumeric ASCII string
containing, in the case of writing
operation,the parameter to input
into the window addressed by
the field <WINDOW>This field
may have variable length
according to the data type
contained in the window where
you are working in. In the case of
reading request of a window, the
data field doesn't exist.
<ETX>= 0x03
<CRC>= XOR among all the characters
following <STX>=(with exception
of <STX>), including the end
character <ETX> hexadecimally
encoded by two ASCII characters.
When a slave device is addressed by the master :
1)
In case of reading request of the value contained in
a window, the slave answers a string equal to the
one sent by the master but in addition there is the
field <DATA>
window.The format of the field <DATA> depends to
the window type.
The different types are :
Lenght
logic 1
analog 6
alphanumeric max 10
EXAMPLES:
Command : START
Source : PC
Destination : Inverter
02 80 30
STX ADDR WINDOW
Source : Inverter
Destination : PC
02 80 06
STX ADDR ACK
59
TECHNICAL INFORMATION
containing the value
Characters permitted
'0'=OFF
,'1'=ON
'-', '-','0'...'9'
( to the right with '0')
' '...'_'
03
30 30 31 31
WR ON ETX
03 38 35
ETX CRC
87-900-883-01 (C)
of the
42 33
CRC