BECKHOFF BK7000 - Manual (Page 27)

Appendix
BK 7000 26
The base addresses I0 and O0 listed here are used as relative addresses
or addresses in the bus coupler. If you have an appropriate superordinate
Profibus system you can use the bus master to enter these addresses at
any desired position in the process image of the control unit. You can use
the configuration software of the master to assign the bytes to the ad-
dresses in the process image of the control unit.
Representation of analog signals in the
process image
In the standard case, the analog signals are presented as follows: to input
bytes or to output bytes of the process image are needed for each analog
channel. The two bytes represent the value as unsigned interger, i.e. 15
bits with the sign. The data format is used independently of the actual reso-
lution. Example: with a resolution of 12 bits in the case of analog values in
the positive and negative value ranges, the four least significant bits are of
no importance. If the value of the analog signal is only positive, the sine bit
(bit 15, MSB) is always "0". In this case, the 12 bits of the analog value are
represented in bit 14 to bit 3. The three least significant bits are of no im-
portance.
By configuration via the Profibus master software or the KS2000 software,
the bus coupler can represent all or individual analog channels in an ex-
tended mode. Optionally, the control and status byte of a channel can also
be inserted. The least significant byte of three bytes has control and status
functions. The other two bytes become inputs and outputs. Various opera-
ting modes can be set with the control byte. The 6 least significant bits of
the control and status byte can be used as addressing bits. Addressing
serves to read and write a register set inside the terminal. The register set
has 64 registers. The settings are stored permanently
I/O bytes of an analog
Output byte 1 Output byte 0 Control byte
channel in the process
image Input byte 1 Input byte 0 Status byte
Significance of the
BIT 7 0 = NORMAL MODE, 1 = CONTROL MODE
control/status bytes BIT 6 0 = READ, 1 = WRITE
for accessing BIT 5 Register address, MSB
the register model BIT 4 Register address
BIT 3 Register address
BIT 2 Register address
BIT 1 Register address
BIT 0 Register address, LSB