PACiS GTW GTW/EN T/C40, Техническое руководство

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GTW/EN CT/C40 Communication
Page 36/64 PACiS Gateway
Query:
Slave
Address Function
Code
= 03
Starting
Address
(H)
Starting
Address
(L)
No. of
Points
(H)
No. of
Points
(L)
CRC
(L)
CRC
(H)
The query message specifies the starting register and the quantity of registers to be read.
Response:
Slave
address Functio
n code
= 03
Byte Count
= <nbytes> Data
(H)
# 1
Data
(L)
# 1
Data
(H)
# i
Data
(L)
# i
Data
(H)
# nbytes/ 2
Data
(L)
# nbytes/2
CRC
(L)
CRC
(H)
The register data in the response message are packed as two bytes per register, with the
binary contents right justified within each byte. For each register, the first byte contains the
high order bits and the second contains the low order bits.
Important notes:
If the starting address is not a point in configuration, the message will not be accepted, and
an error exception 2 will be returned.
If the starting address is in configuration and if there is some “holes” (addresses not in
configuration) theses holes will be padded with the value 0
4.6.1 Signed normalised coding
The signed normalised coding is used to encode the 16 bits-registers. Analogue maximal
value will be coded 7FFFh (decimal value + 32767), and minimal value will be coded 8000h
(decimal value –32768).
For this mode, the gateway may now code the value on 8 to 16 bits [ low part of the register
will be used ]. But, 16 bits is normally the standard to use the full scale conversion.
Example:
In configuration the maximal value for an analogue point is +3000 and minimum value for
this analogue is 0.
That means that when the analogue is received with value 0 from the system, the gateway
will send to the SCADA the register with 8000h value. If this analogue is equal to the
maximal value +3000, the value sent to the SCADA is 7FFFh. Calculation is linear for the
coding between the min and max values.
4.6.2 Unsigned normalised coding
The unsigned normalised coding is used to encode the 16 bits-registers. Analogue maximal
value will be coded FFFFh (decimal value + 65535), and minimal value will be coded 0000h
(decimal value 0).
For this mode, the gateway may now code the value on 8 to 16 bits [ low part of the register
will be used ]. But, 16 bits is normally the standard to use the full scale conversion.
Example:
In configuration the maximal value for an analogue point is +3000 and minimum value for
this analogue is 0.
That means that when the analogue is received with value 0 from the system, the gateway
will send to the SCADA the register with 0h value. If this analogue is equal to the maximal
value +3000, the value sent to the SCADA is FFFFh. Calculation is linear for the coding
between the min and max values.