Burkert Type 1115 - Manual (Page 21)

21
5. RS 232 - Protocol
5.1 Transmission format
8 Bit ASCII
1 Startbit
1 Stopbit
1 Paritybit (if "odd" or "even")
The data is transmitted in IEEE format.
S. E. E. E. E. E. E. E. Value = (-1) S * 2 (E-127) * 1.Mantissa
E. M. M. M. M. M. M. M. S = Sign
M. M. M. M. M. M. M. M. E = Exponent
M. M. M. M. M. M. M. M. M = Mantissa
hex 40 40 00 00 = 1 · 2 · 1,5
A parity check will be carried out ("odd", "even", "none")
In addition, a block check will be carried out.
All bytes are added onto one byte without considering the overflow.
The LSByte of the "block check" symbol is transmitted as the second to last symbol
(before the ETX).
Each block begins with an STX (HEX 2) and ends with an ETX (HEX 3).
STX and ETX are not components of the "block check".
5.2 Transmission protocol
Following each write access the unit answers with ACK (HEX 6) whenever the access
has
been carried out correctly.
The unit answers with NAK (HEX 15) whenever the access could not be carried out
even
through the block was correctly received.
In the event of a transmission error, no answer is given.
If an STX is received within a telegram, then this will result in a new start being carried
out and the former content being lost.
An access is built as follows:
1. Byte address: address of the station MSByte
2. Byte address: address of the station LSByte
3. Byte index: object index MSByte
4. Byte index: object index LSByte
5. Byte value: value MSByte
6. - 13. byte: value according to value length