Beckhoff KL2521 Series, Documentation

Page: 38 / 43

Access from the user program
KL2521 38 Version: 2.1
Byte Byte 3 Byte 2 Byte 1 Byte 0
Name Data out, low byte Data out, high byte Not used Control byte
Value 0x35 0x12 0xXX 0xDF
The code word [
}
32] is set, and the terminal returns the register address with bit 7 for register access as
acknowledgment.
Byte Byte 3 Byte 2 Byte 1 Byte 0
Name Data in, low byte Data in, high byte Not used Status byte
Value 0x00 0x00 0x00 0x9F
5.5 Examples of Register Communication
The numbering of the bytes in the examples corresponds to the display without word alignment.
5.5.1 Example 1: reading the firmware version from Register 9
Output Data
Byte 0: Control byte Byte 1: DataOUT1, high byte Byte 2: DataOUT1, low byte
0x89 (1000 1001
bin
) 0xXX 0xXX
Explanation:
• Bit 0.7 set means: Register communication switched on.
• Bit 0.6 not set means: reading the register.
• Bits 0.5 to 0.0 specify the register number 9 with 00 1001
bin
.
• The output data word (byte 1 and byte 2) has no meaning during read access. To change a register,
write the required value into the output word.
Input Data (answer of the bus terminal)
Byte 0: Status byte Byte 1: DataIN1, high byte Byte 2: DataIN1, low byte
0x89 0x33 0x41
Explanation:
• The terminal returns the value of the control byte as a receipt in the status byte.
• The terminal returns the firmware version 0x3341 in the input data word (byte 1 and byte 2). This is to
be interpreted as an ASCII code:
◦ ASCII code 0x33 represents the digit 3
◦ ASCII code 0x41 represents the letter A
The firmware version is thus 3A.
5.5.2 Example 2: Writing to an user register
Note
Code word
In normal mode all user registers are read-only with the exception of Register 31. In order
to deactivate this write protection you must write the code word (0x1235) into Register 31. If
a value other than 0x1235 is written into Register 31, write protection is reactivated. Please
note that changes to a register only become effective after restarting the terminal (power-
off/power-on).