Uint16; Event - Siemens 7SR45 Argus User Manual

5.2.4

UINT16

The UINT16 is a signed 16 bit integer. As it is an integer, negative numbers are sent as 2's
complement.
UINT16 & MODBUS
In this MODBUS implementation the 16 bit value is stored in a 16 bit register in Big-Endian
format. As an example, if we take the hex representation of 5678 we have 162Eh. Assume
this is stored in the register 30001, it would look as follows:
Address
30001
On reception this register should be interpreted as a 16 bit integer.
Truncation
Calculations are performed as 32 bit. The 16 bit value is the lowest 16 bits of the 32 bit value.
Therefore, when values overflow the returned value is the lowest 16 bits of the calculated
value. For Example, if the value is 85400 = 14D98h, the value returned would be the lowest
16 bits = 4D98h which equals 19864.
5.2.5

EVENT

MODBUS does not define a method for extracting events; therefore a private method has
been defined based on that defined by IEC60870-5-103.
The EVENT register contains the earliest event record available. The event record is 8
registers (16bytes) of information, whose format is described below. When this record has
been read it will be replaced by the next available record. Event records must be read
completely; therefore the quantity value must be set to 8 before reading. Failing to do this will
result in an exception code 2. If no event record is present the exception code 2 will be
returned. The EVENT register should be polled regularly by the master for events.
The EVENTCOUNT register can be checked periodically to determine how many events are
stored.
The format of the event record is defined by the zero byte. It signifies the type of record which
is used to decode the event information. The zero byte can be one of the following.
Format
The format of the event record is defined by the zero byte. It signifies the type of record which
is used to decode the event information. The zero byte can be one of the following.
Type Description
1 Event
2 Event with Relative Time
4 Measurand Event with Relative Time
© 2018 Siemens Protection Devices Limited
Chapter 4 - 7SR45 Data Communications Definitions
Value
162E
Chapter 4 Page 13 of 20