Iskra MC320 User Manual page 72

The output telegram is used to indicate to the MC350H which data module should be returned in the following
input telegram. Output telegram is also used to write values to the MC350H output module registers. Header
byte 0 indicates the module number index being requested. This number (1‐4) tells the MC350H which module
of measuring data should be transferred inside the input telegram which follows next or with number 5 indicates
the output module being written.
Header bytes 1 and 3 are not used. Header byte 2 is used as a control byte to control operation flow as follows:
B7 B6 B5 B4 B3
WR X X X X
Bit 0 when set to 1 tells the MC350H device that it should update internal measuring data which are currently
active on the Profibus exchange telegram. If this bit is set to 0, data are not refreshed on the Profibus network.
Bit 7 when cleared indicates that write operation to the module 5 output registers is being executed. When set
indicates that read operation of the 1‐5 module registers is performed.
In Data bytes section which follows Header byte 4 up to 124 bytes of measuring data for any of the 4 modules
could be included. Module table definition is described in next section.
MC350H input telegram is defined as:
Slave telegram to the Master
Header byte 0
Header byte 1
Header byte 2
Header byte 3
Data bytes 4‐128
Header byte 0 indicates the module number index being requested. With this number (1‐5) MC350H indicates to
the Master which module of data is being transferred inside the SRD data section.
Header bytes 1 and 2 are not used.
Header byte 3 is used as a status byte with the following meaning.
B7 B6 B5 B4 B3 B2 B1 B0
X X X UP X
With bit 4 (UP) set to 1 MC350H indicates to the Master that internal data update is in progress. Value 0 means
that internal data processing completed.
With bit 1 (ID) set to 1 MC350 signalizes to the Master that telegram ID inside the header byte 1 is wrong (not in
the range 1‐5). This prevents errors when addressing wrong input telegrams at the Master output telegram.
64
B2 B1 B0
X X DU
Meaning/contents
telegram ID – or module number of the
returned data segment
reserved‐not used at this time
reserved‐not used at this time
status byte
up to 124 bytes of user data
X ID X
Measuring centres – MC320, MC330, MC350 & MC350H ‐ User's Manual
APPENDIX C: PROFIBUS PROTOCOL
Value
1‐5
XXXUP XXIDX
user data being exchanged