Control and status word

Control word

The control word (CW) is located in the output process image, and is transmitted from the controller to the terminal.

Bit

CW.15

CW.14

CW.13

CW.12

CW.11

CW.10

CW.9

CW.8

CW.7

CW.6

CW.5

CW.4

CW.3

CW.2

CW.1

CW.0

Name

OL7

OL6

OL5

OL4

OL3

OL2

OL1

OL0

-

OL2*

OL1*

OL0*

SC

IR

RA

TR

Bits CW.15 to CW.8 are only shown if the large process image is used.
If the small or medium process image is used, only bits CW.7 to CW.0 are shown as control bytes! The number of output bytes available for transfer from the controller to the terminal is displayed by bits OL2* ... OL0*.

Key

Bit

Name

Description

CW.15
...
CW8

OL7 ... OL0
(OutLenght)

1dec... 22dec

If the large process image is used: Number of output bytes () available for transfer from the controller to the terminal.

-

If the small/medium process image is used: not shown

CW.7

-

0bin

reserved

CW.6 
…
CW.4

OL2* ... OL0*
(OutLenght*)

0

If the large process image is used: reserved

1 ... 6

If the medium process image is used: Number of output bytes available for transfer from the controller to the terminal.

1 ... 4

If the small process image is used: Number of output bytes available for transfer from the controller to the terminal.

CW.3

SC
(SendContinious)

rise

Continuous sending of data from the FIFO.
The send buffer is filled (up to 128 bytes) by the controller. The buffer content is sent with rising edge of bit SC. The terminal acknowledges the data transfer to the controller through setting of bit SW.2. SW.2 is cancelled with CW.3.

CW.2

IR
(InitRequest)

1bin

The controller requests terminal for initialization. The send and receive functions are blocked, the FIFO pointers are reset and the interface is initialized with the values from the relevant registers (R32-R35, R18). The terminal acknowledges completion of the initialization via bit SW.2 (IA).

0bin

The controller once again requests the terminal to prepare for serial data exchange.

CW.1

RA
(ReceiveAccepted)

toggle

The controller acknowledges receipt of data by changing the state of this bit. Only then new data can be transferred from the terminal to the controller.

CW.0

TR
(TransmitRequest)

toggle

Via a change of state of this bit the controller notifies the terminal that the DataOut bytes contain the number of bytes indicated via the OL bits. The terminal acknowledges receipt of the data in the status byte via a change of state of bit SW.0 (TA). Only now new data can be transferred from the controller to the terminal.

Status word

The status word (SW) is located in the input process image, and is transmitted from terminal to the controller.

Bit

SW.15

SW.14

SW.13

SW.12

SW.11

SW.10

SW.9

SW.8

SW.7

SW.6

SW.5

SW.4

SW.3

SW.2

SW.1

SW.0

Name

IL7

IL6

IL5

IL4

IL3

IL2

IL1

IL0

-

IL2*

IL1*

IL0*

BUF_F

IA

RR

TA

Bits SW.15 to SW.8 are only shown if the large process image is used.
If the small or medium process image is used, only bits SW.7 to SW.0 are shown as status bytes! The number of input bytes available for transfer from the terminal to the controller is displayed by bits IL2* ... IL0*.

Key

Bit

Name

Description

SW.15
...
SW8

IL7 ... IL0
(InLenght*)

1dec ... 22dec

If the large process image is used: Number of input bytes available for transfer from the terminal to the controller.

-

If the small/medium process image is used: not shown

SW.7

-

0bin

reserved

SW.6
...
SW.4

IL2* ... IL0*
(InLenght*)

0

If the large process image is used: reserved

1 ... 6

If the medium process image is used: Number of input bytes available for transfer from the terminal to the controller.

1 ... 4

If the small process image is used: Number of input bytes available for transfer from the terminal to the controller.

SW.3

BUF_F

1bin

The receive FIFO is full. All further incoming data will be lost!

SW.2

IA
(InitAccepted-Bit)

1bin

Initialization was completed by the terminal.

0bin

The terminal is ready again for serial data exchange.

SW.1

RR
(ReceiveRequest)

toggle

Via a change of state of this bit the terminal notifies the controller that the DataIn bytes contain the number of bytes indicated via the IL bits. The controller has to acknowledge receipt of the data in the control byte via a change of state of bit CW.1 (RA). Only then new data can be transferred from the terminal to the controller.

SW.0

TA
(TransmitAccepted)

toggle

The terminal acknowledges receipt of data by changing the state of this bit. Only now new data can be transferred from the controller to the terminal.

Data transfer examples

The examples use the large process image.

Data transfer from the controller to the terminal

Control word

Status word

Comment

CW.15 ... CW.8

CW.7 ... CW.1

SW.15 ... SW.8

SW.7 ... SW.1

0000 0000bin

0000 0000bin

xxxx xxxxbin

0000 x0x0bin

Start of data transmission

0000 0010bin

0000 0001bin

xxxx xxxxbin

0000 x0x0bin

The controller requests transmission of 2 bytes by the terminal

0000 0010bin

0000 0001bin

xxxx xxxxbin

0000 x0x1bin

Command is executed: Terminal has loaded 2 bytes into the transmission FIFO

0001 0000bin

0000 0000bin

xxxx xxxxbin

0000 x0x1bin

The controller requests transmission of 16 bytes by the terminal

0001 0000bin

0000 0000bin

xxxx xxxxbin

0000 x0x0bin

Command is executed: Terminal has loaded 16 bytes into the transmission FIFO

Data transfer from the terminal to the controller

Control word

Status word

Comment

CW.15 ... CW.8

CW.7 ... CW.1

SW.15 ... SW.8

SW.7 ... SW.1

xxxx xxxxbin

0000 000xbin

0000 0000bin

0000 000xbin

Start of data transmission

xxxx xxxxbin

0000 000xbin

0000 0011bin

0000 001xbin

The terminal requests transfer of 3 bytes from the controller

xxxx xxxxbin

0000 001xbin

0000 0011bin

0000 001xbin

Acknowledgement: Controller has received 3 bytes from the receive FIFO

xxxx xxxxbin

0000 001xbin

0001 0110bin

0000 000xbin

The terminal requests transfer of 22 bytes from the controller

xxxx xxxxbin

0000 000xbin

0001 0110bin

0000 000xbin

Acknowledgement: Controller has received 22 bytes from the receive FIFO

Initialization

Control word

Status word

Comment

CW.15 ... CW.8

CW.7 ... CW.1

SW.15 ... SW.8

SW.7 ... SW.1

xxxx xxxxbin

xxxx xxxxbin

xxxx xxxxbin

xxxx xxxxbin

Start of data transmission

0000 0000bin

0000 0100bin

0000 0000bin

0000 0000bin

The controller requests terminal initialization

0000 0000bin

0000 0100bin

0000 0000bin

0000 0100bin

Command is executed: Terminal initialization is complete

0000 0000bin

0000 0000bin

0000 0000bin

0000 0100bin

The controller requests the terminal to prepare for serial data exchange

0000 0000bin

0000 0000bin

0000 0000bin

0000 0000bin

Command is executed: Terminal is ready for serial data exchange