S.B.C. Elettronica S.p.A. - Engineering Division
HPDxxN – High Power User’s Manual
73
4 - 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. It is also possible to set transmission speed 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
HPD N drives.
Refer to the heading
Serial line connection
for connection diagrams.
4.1 Communication 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]
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
