Parker LVD1 - Page 76

Parker Hannifin S.p.A. - Divisione S.B.C. LVD User’s Manual
76
[STX] = $7E transmission start indicator. If a field other than STX should assume the value
$7E in the message, this field is followed by a zero ($00) to ensure that it cannot be
interpreted as an [STX].
[CMD+ADDR] = command and address of peripheral device, always different from zero.
This datum is composed as follows: the first 5 bits (from 0 to 4) define the drive address (from
0 to 31); the remaining 3 bits (from 5 to 7) define the type of message, as described in the
following table:
[LUN] = number of bytes of transmitted datum (parameter or PLC instruction); can assume
values from 1 to 4. This value must not hold zero characters ($00) after values that coincide
with the transmission start character ($7E).
[PAR] = parameter or PLC instruction read/write address.
[D0]... [Dn] = transmitted datum.
[CHK] = 256 modulus sum of all fields excluding [STX] (checksum).
Message types
[CMD1] = is the drive's answer to a data request; the answer message has the following
format:
[STX] [001+ADDR] [LUN] [PAR] [D0]... [Dn] [CHK]
can also be a message confirming a write or data modification operation; in this case the
format is as follows:
[STX] [001+ADDR]
where ADDR always identifies the answering drive.
[CMD2] = read message relative to an instruction in the PLC area; format:
[STX] [010+ADDR] [LUN] [PAR] [CHK]
[CMD3] = write message relative to an instruction in the PLC area; format:
[STX] [011+ADDR] [LUN] [PAR] [D0]... [Dn] [CHK]
[CMD4] = parameter read message; format:
[STX] [100+ADDR] [LUN] [PAR] [CHK]
[CMD5] = parameter write message; format:
[STX] [101+ADDR] [LUN] [PAR] [D0]... [Dn] [CHK]
[CMD6] = byte parameter bit change message; format:
[STX] [110+ADDR] [LUN] [PAR] [D0] [D1] [CHK]
CMD bit 7 bit 6 bit 5 message type
1 0 0 1 drive response
2 0 1 0 read pico-PLC instruction
3 0 1 1 write pico-PLC instruction
4 1 0 0 read parameter
5 1 0 1 write parameter
6 1 1 0 change bit
7 1 1 1 broadcast parameter to all slaves