5
1
Description
The Modbus Options Module adds multi-drop serial communications to any stan-
dard GIMA meter. The device uses a high-speed microprocessor to extract infor-
mation from the meter and interface to an industry-standard Modbus system.
Use of a dedicated communications processor ensures optimum efficiency, allow-
ing fast access to data on systems with multiple meters. The use of Modbus
protocol ensures compatibility with existing systems and/or a number of readily
available software packages.
The Options Module may be configured as RS-485 or RS-232, providing 2 or 4-
wire communications over distances up to 1200 meters. Data rates of 4800, 9600,
or 19200 may be selected to suit system requirements.
Figure 1.1. Options Module
1.1
Available Parameters
The Options Module is available in two forms.
The “Standard” unit provides access to GIMA measure parameters, which may be
seen on the meter’s LCD display. Parameters not provided on a particular GIMA
meter type are set to zero in the Modbus tables (refer to section 4.5).
The “All Value” unit provides access to all parameters shown in the table in section
4.5.
Both types of Options Units provide access to standard programmable meter set-
tings, such as CT primary.
28
Exception Response
EXCEPTION FUNCTION CODE
All normal function types have a most significant bit of 0 (<80 Hex). In an Excep-
tion Response, the meter sets the MSB to 1 (adds 80H to the received Function
Type). The Function can therefore be used by the host to detect an Exception
Response.
DATA FIELD
In an Exception Response, the data field is used only to return the type of error
that occurred (
Exception Code
).
The GIMA Options Unit uses the following Exception Codes:
E
T
Y
B
E
L
P
M
A
X
E
S
S
E
R
D
D
A
R
E
T
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M
1
H
9
1
N
O
I
T
C
N
U
F
2
H
4
8
E
D
O
C
N
O
I
T
P
E
C
X
E
3
H
2
0
)
e
t
y
B
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H
(
M
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C
E
H
C
4
H
2
4
)
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t
y
B
w
o
L
(
M
U
S
K
C
E
H
C
5
H
6
C
E
D
O
C
G
N
I
N
A
E
M
1
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