APS 6RL Series, Руководство по эксплуатации

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6RL SERIES OPERATION MANUAL
SECTION 7: REMOTE PROGRAMMING
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2018 by Adaptive Power Systems, Inc. (APS) • All Rights Reserved • No reproduction without written authorization from APS.
6RL Series Regenerative DC Load Operation Manual Page 120 of 204
7.5 ModBus Protocol
7.5.1 Preface
Before referencing this section, make sure the interface module option installed in the
power source supports the ModBus protocol.
The 6RL Series are always ModBus slaves with address zero (0). This setting cannot be
changed.
7.5.2 General ModBus RTU Information
A telegram (or message) as defined by the ModBus RTU protocol consists of hexadecimal
bytes, of which the first byte, the ModBus address, must always be 0. The first byte of a
telegram is used to distinguish the telegram between ModBus and SCPI. A value between 1
and 41 in the first byte will cause a ModBus communication error, whereas from 42 (ASCII
character: *) the telegram is interpreted as a text message or SCPI command.
Format and length of a telegram are defined. The telegram has to be transmitted according
to the specifications of the particular interface that is used. Normally, the user only has to
ensure a correct message, rather than correct transmission. But there are also interfaces,
like for example RS232, which do no feature communication protocol handling and do not
guarantee transmission. Other interfaces support guaranteed correct transmission by using
a check- sum and/or software handshaking.
7.5.3 General ModBus TCP Information
The message protocol according to ModBus TCP/IP standard (short: ModBus TCP) is only
available with the ModBus TCP 1-Port and 2-Port interface modules and only via the default
ModBus TCP port 502. By definition, a ModBus TCP message requires an additional header
of 6 or 7 bytes, compared to ModBus RTU. This makes it impossible to use SCPI commands
via this port. The rest of the message is identical to ModBus RTU, except for the checksum at
the end, which is not necessary with ModBus TCP. Information about the header can be
found below. The following sections are related to the core part of ModBus messages,
which is identical for both protocols. Also see section 7.10, “ModBus TCP Details” on page
131 for details.
7.5.4 Format of set values and resolution
Set values, as transmitted via digital interfaces, are always percent values of the unit’s
nominal values (U, I, P, R) and correspond at 100% to the hexadecimal value 0xCCCC
(decimal: 52428). The total usable range is 0%...102% (0x0000...0xD0E5). The register lists
for a particular series defines the range for all settable values.
It means, you can set a percent value between 0% and 100% by sending hexadecimal values of
0x0000-0xCCCC resp. for supervision thresholds of unit alarms like OVP it will be 0x0000-
0xE147 for 0% to 110% or on some series 0x0000-0xD2F1 for 0 to 103%.