A3 Irda Data Bits - Elster A1100 Operating & Maintenance Instructions

Electronic polyphase meter

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A1100 - Electronic Polyphase Meter

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 = 00000001b => 01010111b = 57h

05h = 00000101b => 01110111b = 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)

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