Burkert Type 8644 - Manual (Page 109)

8644/phoenix - 105
S
YSTEM
D
ESCRIPTION
Input and output data
The pressure measurement module is controlled via 2 bytes of input data and 2 bytes of output data.
The first byte is the control byte of the output data (master) and the status byte of the input data (master).
In normal operation the status byte corresponds to the response of the control byte of the previous
interrogation.
The second byte is the data byte.
Master PMM
data byte (2)
data byte (2)
control byte (1)
control byte (1)
Control byte
The difference between the process and parametrization data is determined by the status bit of the control
byte.
Status bit 0 → process cata
Status bit 1 → parametrization data
Process data
Process data transmits the pressure value 1) of the system and the units set up in the module.
Calling up process data
When you call up process data, the control byte must assume a value between 0x00 and 0x7F
(status bit = 0). The data byte is not taken into account.
The status byte of the response depends on the unit set on the local display.
The data byte supplies the pressure value
1) .
Unit Status byte
on display of response
bar
→
0x38
kPa → 0x39
psi
→
0x3A
1) Pressure value: value in bar x 10 (without decimal point)
Structure of the control byte
AS: status bit (process or parametrization data)
FB: error bit
15-10: bits containing further information
AS FB 15 14 13 12 11 10