KROHNE CORIMASS MFC 85 Interface EN - Manual (Page 18)

18
7. Format of the data field
The data field format for Bus transmission is as follows:
DEV ADR VER FKT < Parameter - Field >
The device code byte (DEV) recognises the unique code assigned to the particular type of
KROHNE device connected to the Bus. For MFC 085 this code is OAO hex, and OA1 for the
MFC 081.
The address byte (ADR) contains the bus address of the requested device. Values from 0 to
239 (0 hex to 0EF hex) are permissible. Addresses 240 to 255 are reserved for special
functions.
The version byte (VER) is relevant only for acknowledgement purposes. In a
acknowledgement request it may be set to an arbitrary value. This field is a composite one:
bits 5 - 7 define the version number of the device software, bits 0 - 4 subversion number, e.g.
a device with version 3.15 Software will acknowledge in VER field as 6F hex.
The function byte (FKT), like the VER byte, is also split into two fields: bits 5 - 7 define a
generalised function which will later on be referred to as Function, while bits 0 - 5 define
additional identification information being either a logical address of a device data block or
descriptor of a special request to device (like calibration, quit errors, etc.). These latter 5 bits
will later be referred to as Subfunction. For complete list of FKT-driven functionality refer to
the Function Byte Codes table in the protocol manual.
Device response time depends on requested operation:
•
Read measurement block
≈
20 msec
•
Read single static block
≈
5 msec
•
Write single block
≈
200 msec
•
Write two blocks
≈
400 msec
In a case where a special operation is requested that deals with complete device reset, bus-
connection will be lost until the instrument bypass re-initialisation.