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4.2.8 STR32 & STR64
4.2.9 BITSTRING
A Bit-String (or Bit-Array) is a method of compactly storing a number of bits of data. In this instance we store
up to 16 bit values, for example the states of binary inputs, in a single 16 bit register. The first bit value is
stored in the Least Significant Bit (LSB) of the register. The 16
(MSB). Bit values can only be zero or one. Any unused bits will be set to zero.
BITSTRING & MODBUS
In this MODBUS implementation the 16 bit value is stored in a 16 bit register in Big-Endian format.
As an example, assume bits 1, 3, 9 and 12 are set. The binary representation of this would be
0000100100000101
30001, it would look as follows:
On reception this register should be interpreted as a 16 bit integer.
© 2013 Siemens Protection Devices Limited
Byte
0
1
2
ms L ms H
Mi
Time Format.
giving a hex representation of 0905h. Assume this is stored in the register
2
Address
30001
Chapter 4) 7SR17 Rho - Data Communications
3
4
5
6
Ho
Da
Mo
Ye L Ye H
th
value would be in the Most Significant Bit
Value
0905
7
Chapter 4 - Page 27 of 75
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