BARTEC BENKE HYGROPHIL H 4230-12 Ex Zone II, Руководство по эксплуатации, Страница: 110 / 112

PROFIBUS
104
Operating Instructions HYGROPHIL® H 4230-12 BA 060207
8.4 Examples
Two sample sequences will be used to illustrate how to read from HYGRO-
PHIL H (querying the dew point) and how to write to HYGROPHIL H (chang-
ing to standby mode).
8.4.1 Reading from HYGROPHIL H
Querying the dew point
According to the channel description the dew point can be found at data ad-
dress 0x20 with offset 0. Due to the fact that it is a float value, 4 bytes of in-
formation need to be requested.
Read request from the PROFIBUS master:
0x02 0x00 0x0020 0x0000 0x04
Byte 0
Command code
Byte 1
Reserved
Bytes 2/3
Data address
Bytes 4/5
Offset
Byte 6
Data length
Byte 0: Command code for a read process (Read = 0x02 )
Byte 1: Reserved ( must always be 0x00 !!)
Data address from channel description:
Byte 2: 0x00
Byte 3:
0x20
for dew point
Offset from channel description:
Byte 4: 0x00
Byte 5: 0x00
Length of the data requested:
Byte 6: 0x04 for 4 bytes
Response from HYGROPHIL:
0x80 0x00 0x0020 0x0000 0x04 0x00 0xXX
Byte 0
Status code
Byte 1
Reserved
Bytes 2/3
Data address
Bytes 4/5
Offset
Byte 6
Data length
Byte 7
Reserved
Bytes 8...11
User data
Byte 0: Status code for a successful 0x80 read access
Byte 1: 0x00 (reserved)
Data address from channel description:
Bytes 2/3: Data address of the requested value (here 0x0020 for dew
point)
Offset from channel description:
Bytes 4/5: Offset of the requested value (here 0x0000 for dew point)
Length of the data transmitted:
Byte 6: 0x04 for the float value of the dew point
Byte 7: Reserved
Bytes 8...11: Float value of the dew point in line with IEEE 754 Floating Point
Standard
Bit 0 of the first byte of the float is sent first.