Siemens TC63 Benutzerhandbuch

s

TC63_ATC_V00.490

Page 453 of 501

5/24/05

Confidential / Draft - Do not copy

This section provides information on the protocol used for data transmission to or from I²C devices and explains

the data mode. It is assumed that you are familiar with the I²C specification. 

Throughout this section the following document conventions are used to mark the direction of send and receive:

Transfer Message: AT 

→  I²C device driver 

Response Message: AT 

←  I²C device driver 

To change from command mode to data mode use the 

 write command. To close down the channel

and return to command mode send the ASCII code # (0x23). 

The protocol allows using a Terminal program for the communication between the module and the I²C slave

device. To visualize transferred characters and response data it is recommended to run the Terminal program

in chat mode or to switch on local echo. 

For transfer and response, special characters are defined, such as Start and Stop to mark a single message and

Close to disconnect the data channel. All valid special characters are listed below: 

Table 19.3:  Special characters for ASCII coding

Direction

AT - Driver

Function in protocol

Special

character

Hex value

Description

→

Start Transfer Message

<

0x3C

Special character sent to the I²C  driver to 

start sending.

→

Stop Transfer Message

>

0x3E

Special character sent to the I²C  driver to 

stop sending.

→

Channel Close

#

0x23

For signalling.

Channel Close can be sent any time inside 

or outside a transmit or receive message. 

Causes the transfer to be aborted and 

takes the ME back to AT command mode.

←

Start Response Message {

0x7B

Special character sent to the I²C  driver to 

mark the beginning of a Response Mes-

sage.

←

Stop Response Message }

0x7D

Special character sent to the I²C  driver to 

mark the end of a Response Message.

←

Protocol error

!

0x21

For signalling.

Reports to the AT interface that the Trans-

fer Frame does not comply with the proto-

col definition (syntax error).

←

Transmission OK

(in I²C protocol referred to 

as ACK)

+

0x2B

Notifies the AT interface that data were 

successfully transmitted or the I²C Slave 

Address was recognized. 

←

Transmission error

(in I²C protocol referred to 

as NAK)

-

0x2D

Notifies the AT interface that data transmis-

sion failed or the I²C Slave Address was 

not recognized. On the I²C bus, the faulty 

data byte (16 bit byte counter) is identified 

as well.