Elster A1100, Инструкция по эксплуатации и обслуживанию, Страница: 42 / 51

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A1100 - Electronic Polyphase Meter
©
Elster Metering Systems - M180 001 1E - 6.2005
A3 IrDA Data Bits
Each serial word transmitted contains eight data bits plus the Start and Stop bits.
These data bits actually only represent one nibble, four bits, of real data – these bits are interspersed
with a logic‘1’ to achieve the logic‘1’ to logic‘0’ transition thereby creating an infra-red pulse when a
real data bit is logic‘0’.
Consequently, a real data byte of 8 bits is transmitted as two serial words. The low nibble is
transmitted first, followed by the high nibble.
For example, if the real data byte is 51h then the transmitted data will be two serial words
representing 01h followed by 05h , but since the bits within the nibbles are separated by logic‘1’s the
actual transmitted data will be:-
01h = 0000 0001 b => 0 1 0 1 0 1 1 1b = 57h
05h = 0000 0101 b => 0 1 1 1 0 1 1 1b = 77h
Note that the bits are actually transmitted least significant bit first – thereby the first data bit is always
a logic’1’.
Transmission Translation Table :-
Data Nibble (4 bit hex) Transmitted Data (8 bit hex)
0 55
1 57
2 5D
3 5F
4 75
5 77
6 7D
7 7F
8 D5
9 D7
A DD
B DF
C F5
D F7
E FD
F FF