Parker Hannifin S.p.A. - Divisione S.B.C. LVD User’s Manual
75
5 SERIAL INTERFACE
The drive communication protocol is "master-slave" half-duplex type on an asynchronous
RS-485/RS-422 line. The drives assume control of the line only following interrogation by
the master.
Up to 32 drives can be connected on the same serial line, allocating each a different serial
address in parameter Pr27. Transmission speed can be programmed in parameter Pr26 as
specified in the table:
(*) The version with code Pr26=4 differs from Pr26=5 because of the 25 ms response delay.
This version was developed to interface with PLCs that require this characteristic.
(**) The version with code Pr26=10 was developed to allow data communication between
two LVD drives.
Refer to the heading Serial line connection for connection diagrams.
5.1 Communications protocol
The right hand column in the table shows the time-out value in milliseconds for each
communication speed; this is the time, starting from the beginning of each message (STX)
within which the transmission of the message must terminate. Therefore, if the message is
interrupted, after the time-out the drive will ignore the information already received and stand
by to receive a new message.
Messages are made up of several consecutive data in the following format:
1 start bit
8 data bits following one byte between square brackets
1 parity bit (even)
1 stop bit
The message structure is:
[STX] [CMD+ADDR] [LUN] [PAR] [D0]... [Dn] [CHK]
where:
Pr26 (decimal base) b/s time-out (ms)
0 600 512
1 1200 256
2 2400 128
3 4800 64
4 9600 (*) 32
5 9600 32
6 19200 16
7 38400 12
8 57600 8
9 125000 4
10 57600 (**) 8
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