CTT2 protocol

The CTT2 protocol is structured as follows:

00

01

02

03

04

05

...

CTT2 service

Data

00

01

02

03

00

01

...

Code

[Index]

[Read length]

[Write length]

[Data bytes]

The individual bytes contain the following information:

Byte

Description

Code

  • Request message: Specifies the service of the CTT2 protocol (see chapter CTT2 services).
  • Response message: Indicates the status of the request message (see chapter CTT2 services).

[Index]

Optional. Only for Request message.

Specifies how the CTT2 service is interpreted by the AS-Interface device.

Only the following values are supported by SEW‑EURODRIVE inverters:

  • 0x00 = Device ID
  • 0x03 = SPA protocol

[Read length]

Optional. Depending on the code and [index].

Specifies the number of data bytes for the Response message.

[Write length]

Optional. Depending on the code and [index].

Specifies the number of data bytes for the Request message.

[Data bytes]

Optional. Depending on the code and [index].

Contains the data of the Request message or Response message:

  • in the event of parameter access this is the 12-byte long data packet of the SPA protocol
  • in the event of faulty execution of the CTT2 service this is the CTT2 error code
Additional information