Beckhoff KL4494, Manual

Page: 36 / 40

Access from the user program
KL4494 36 Version: 2.0.0
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).
I. Write the code word (0x1235) into Register 31.
Output Data
Byte 0: Control byte Byte 1: DataOUT1, high byte Byte 2: DataOUT1, low byte
0xDF (1101 1111
bin
) 0x12 0x35
Explanation:
• Bit 0.7 set means: Register communication switched on.
• Bit 0.6 set means: writing to the register.
• Bits 0.5 to 0.0 specify the register number 31 with 01 1111
bin
.
• The output data word (byte 1 and byte 2) contains the code word (0x1235) for deactivating write
protection.
Input Data (answer of the bus terminal)
Byte 0: Status byte Byte 1: DataIN1, high byte Byte 2: DataIN1, low byte
0x9F (1001 1111
bin
) 0xXX 0xXX
Explanation:
• The terminal returns a value as a receipt in the status byte that differs only in bit 0.6 from the value of
the control byte.
• The input data word (byte 1 and byte 2) is of no importance after the write access. Any values still
displayed are invalid!
II. Read Register 31 (check the set code word)
Output Data
Byte 0: Control byte Byte 1: DataOUT1, high byte Byte 2: DataOUT1, low byte
0x9F (1001 1111
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 31 with 01 1111
bin
.
• The output data word (byte 1 and byte 2) has no meaning during read access.
Input Data (answer of the bus terminal)
Byte 0: Status byte Byte 1: DataIN1, high byte Byte 2: DataIN1, low byte
0x9F (1001 1111
bin
) 0x12 0x35
Explanation:
• The terminal returns the value of the control byte as a receipt in the status byte.