BECKHOFF KL6051 - Manual (Page 13)

Data transfer, function
KL6051 13
A further example
Writing register 31 in the BK2000 with an intelligent terminal and the end
terminal.
If the following bytes (user code word) are transferred from the controller to
the terminal,
Byte0
Control
Byte1
Not used
Byte2
Data OUT, high byte
Byte3
Data OUT, low byte
0xDF 0xXX 0x12 0x35
the user code word is set and the terminal returns the register address with
the bit 7 for register access and the acknowledgement.
Byte0
Status
Byte1
Not used
Byte2
Data IN, high byte
Byte3
Data IN, low byte
0x9F 0x00 0x00 0x00
Data transfer, function
8 data bits, 1 start bit, 1 stop bit, even parity
Data containing errors is not transferred to the controller. The processed
data is still valid when the CHK, OVR or PAR date is set. These bits merely
represent the quality of data transfer.
Status byte in
the process data mode
MSB
REG=0 RCVT1 RCVT2 CHK OVR PAR
PAR: parity error or invalid data frame
OVR: buffer overflow
CHK: invalid checksum
RCVT2: the partner terminal has an RCD timeout
RCVT1: the terminal is not receiving any data from the partner. The termi-
nal has set the controller inputs to zero.
For use without status information, the data transfer link can be monitored
from the other respective side of the link by means of a bit set by the cont-
roller. Data transfer of the KL6051 is checked by a watchdog. Thus, failu-
res of the field buses or of data transfer between the KLK6051 units are
easily recognizable.