Siemens SIRIUS 3RK3 - CTT2 Data Exchange

7.6.5 CTT2 data exchange
Using CTT2 code 29 (1D
H
), data sets can be read out from the AS-i through the CTT2 channel
while carrying useful data. The read request must be acknowledged positively (= CTT2 code
5D
H
) or negatively (= CTT2 code 9D
H
) by the AS-i slave within a certain time. Transmission of the
data set requested by the AS-i slave with the speci󹪝ed length is evaluated as a positive
acknowledgment.
Diagnostics with CTT2 codes
The "Write/Read a data set" command is provided in the transmit bu󹪜er. The 󹪝rst three bytes
(command header) contain the command code, slave address, and number of CTT2 bytes. The
CTT2 data set follows this. The CTT2 data set starts with the CTT2 command code, the data set
number, and the data set length, followed by the data set bytes DS byte 0 to DS byte 13.
The DP command interface for the AS-i master accepts the data set bytes and forwards them to
the addressed slave. These data are transmitted using the CTT2 protocol. MSS 3RK3 processes
the CTT2 data set and prepares the requested data and answers using the CTT2 protocol. The AS-
i master accepts the response and forwards it to the receive bu󹪜er of the CPU via the DP
command interface. The response is decoded in the receive bu󹪜er of the CPU and the program
is executed accordingly.
The following responses are possible:
• 5D
H
: Transmission without error (see Chapter "Element messages (Page 312)")
• 9D
H
: Transmission with error, (CTT2 code that is not supported, see Chapter "Error codes
"CTT2 error code" (Page 309)")
• 5A
H
: Transmission with error (CTT2 error data set error, see Chapter "Error codes "CTT2 error
code" (Page 309)")
1. Example of transmission without error
The 󹪝rst example below demonstrates the writing of a data set using data set DS3 "Command
interface: Element accesses," with error-free transmission.
2. Example of transmission with error because of incorrect DS number
The second example below demonstrates the writing of a data set using data set DS3 "Command
interface: element accesses" when there is a transmission error due to incorrect data set number
(DS 4).
Diagnostics / service
7.6 Diagnosis using AS-Interface (CTT2 protocol)
SIRIUS 3RK3 Modular Safety System
Equipment Manual, 07/2020, NEB926253002000/RS-AC/006 303