Eurotherm 6100, User Manual

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100/180MM DISTRIBUTED GRAPHIC RECORDER: USER GUIDE
HA029324
Issue 11 Oct 14 User Guide
Page 314
FFF0
0500
FFF1
FFF2
FFF3
FFF4
6100 or 6180
0001
CC26
HHHH
Product ID
Version ID
FIT start address
Checksum
Company ID
Byte 0
Transaction
identifier
(usually 00)
Transaction
identifier
(usually 00)
Protocol
identifier
(00)
Protocol
identifier
(00)
Byte 1 Byte 2 Byte 3 Byte 4
Number of
bytes fol-
lowing
Byte 5
Always 00
Byte 6
Recorder
Modbus
address
Byte 7
Modbus
function
code (hex)
Bytes 8 onwards
Data
(Depends on
function code)
8.4.9 Permanent ID table
This table contains information relating to the recorder, and also gives the start address of the feature identi fi -
cation table (FIT).
Table 8.4.9 Permanent ID table
8.5 DATA TRANSMISSION
Each message (request or response) is packaged in the (MODBUS) frame shown below. The messages consist
of a 7 byte pre fi x, followed by the function code (in hex), followed by the relevant data bytes, the number and
content of which depend on the function code, as described in subsequent sections.
Figure 8.5 MODBUS package
Notes:
1. The transaction identi
fi er has no active function - the recorder just copies the bytes from the re-
quest message to the response message.
2. The protocol identi fi er bytes are always zero.
FUNCTION CODES AND EXCEPTION CODES
Refer to section 8.2.1 for lists of function codes and exception codes supported.
TEXT STRINGS
When sending text strings, such as Batch fi elds, the fi nal character must be followed by one or two ‘Null’ char-
acters. The number of bytes in the text string (including the null) must be even, even if this means adding two
nulls at the end of the message instead of one.
For example, the text string: “Batch Number’ should be sent as
BatchSpace Number NullNull
, or
BatchSpace Number SpaceNull
where each pair of characters occupies on 16-bit word. Similarly, the text string ‘Batch Number:’ would be
sent as
BatchSpace Numb er :null
,
but only one Null character is required to provide an even number of bytes.