Acyclical channel

Overview

INFORMATION

If you use the acyclical channel to write to objects that are mapped in the I/O area, their values are overwritten with the next cycle. Therefore, data that is mapped in the I/O area should not be written via the acyclical channel!

You can execute write and read commands acyclically via the acyclical channel. Data areas for acyclical communication were implemented in the input/output area of the function module for this purpose. This area comprises 8 bytes of output data and 8 bytes of input data. They have the following assignments:

Request		Response
Output data Byte 0: CMD – Command Byte 1: SUBIDX – Subindex Byte 2: IDX0 – Index (low byte) Byte 3: IDX1 – Index (high byte) Byte 4: DATA0 – Data (low byte) Byte 5: DATA1 – Data Byte 6: DATA2 – Data Byte 7: DATA3 – Data (high byte)	→ ←	Input data Byte 0: STATUS – Status Byte 1: SUBIDX – Subindex Byte 2: IDX0 – Index (low byte) Byte 3: IDX1 – Index (high byte) Byte 4: DATA0 – Data (low byte) Byte 5: DATA1 – Data Byte 6: DATA2 – Data Byte 7: DATA3 – Data (high byte)

Request

Response

Output data

Byte 0: CMD – Command

Byte 1: SUBIDX – Subindex

Byte 2: IDX0 – Index (low byte)

Byte 3: IDX1 – Index (high byte)

Byte 4: DATA0 – Data (low byte)

Byte 5: DATA1 – Data

Byte 6: DATA2 – Data

Byte 7: DATA3 – Data (high byte)

→

←

Input data

Byte 0: STATUS – Status

Byte 1: SUBIDX – Subindex

Byte 2: IDX0 – Index (low byte)

Byte 3: IDX1 – Index (high byte)

Byte 4: DATA0 – Data (low byte)

Byte 5: DATA1 – Data

Byte 6: DATA2 – Data

Byte 7: DATA3 – Data (high byte)

CMD	IDLE→		Command→		IDLE→
Status:		←IDLE		←Command		←IDLE

CMD – Command

Code	Name	Description
0x00	IDLE	Set no-load operation. You can use this command to request the wait status for a new command after the command execution has been reported back via STATUS.
0x11	READ_ONCE	Read a data object You can use this command to request the data once after the command has been recognized.
0x21	WRITE_ONCE	Write a data object You can use this command to write the data only once after the command has been recognized.

Code

Name

Description

0x00

IDLE

Set no-load operation.

You can use this command to request the wait status for a new command after the command execution has been reported back via STATUS.

0x11

READ_ONCE

Read a data object

You can use this command to request the data once after the command has been recognized.

0x21

WRITE_ONCE

Write a data object

You can use this command to write the data only once after the command has been recognized.

SUBIDX – Subindex: Subindex in the object list

IDX0 / IDX1 – Index: Index in the object list

DATA0 – DATA3 – Data: Data to be transferred

STATUS – Status

Code	Name	Description
0x00	IDLE	No-load operation – waits for commands
0x14	READ_ONCE	READ_ONCE command was recognized, data is valid.
0x24	WRITE_ONCE	WRITE_ONCE command was recognized, data was accepted.
0x81	READ_NOT_EXIST	Error – Read access – Data not available Command was not executed!
0x91	WRITE_NOT_EXIST	Error – Write access – Data not available Command was not executed!
0x92	WRITE_RNG_ERR	Error – Write access – Data range exceeded Command was not executed!
0x93	WRITE_RDO_ERR	Error – Write access – Data is read-only Command was not executed!
0x94	WRITE_WPR_ERR	Error – Write access – Data is write-protected Command was not executed!
0x99	ACYC_COM_ERR	Error during acyclical communication Command was not executed!