Register communication

Register access via process data exchange

Control byte in register mode (REG=1)

MSB

REG=1

W/R

A5

A4

A3

A2

A1

A0

REG = 0bin: Process data exchange
REG = 1bin: Access to register structure

W/R = 0bin: Read register
W/R = 1bin: Write register

A5..A0 = register address
Addresses A5...A0 can be used to address a total of 64 registers.

Register communication 1:
Register mode control byte

The control or status byte occupies the lowest address of a logical channel. The corresponding register values are located in the following 2 data bytes. (The BK2000 is an exception: here, an unused data byte is inserted after the control or status byte, and the register value is therefore placed on a word boundary).

Example 1:
Reading of register 8 in the BK2000 with a KL3312 and the end terminal:

If the following bytes are transferred from the controller to the terminal,

Byte

Byte 3

Byte 2

Byte 1

Byte 0

Name

DataOUT 1

DataOUT 0

Not used

Control byte

Value

0xXX

0xXX

0xXX

0x88

The terminal returns the following type identifier (0x0CF0 corresponds to unsigned integer 3312)

Byte

Byte 3

Byte 2

Byte 1

Byte 0

Name

DataIN 1

DataIN 0

Not used

Status byte

Value

0x0C

0xF0

0x00

0x88

Example 2:
Writing of register 31 in the BK2000 with an intelligent terminal and the end terminal:

If the following bytes (code word) are transferred from the controller to the terminal,

Byte

Byte 3

Byte 2

Byte 1

Byte 0

Name

DataOUT 1

DataOUT 0

Not used

Control byte

Value

0x12

0x35

0xXX

0xDF

The code word 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

DataIN 1

DataIN 0

Not used

Status byte

Value

0x00

0x00

0x00

0x9F