Combined transaction types

Combined Transaction Types (CTT) were introduced in specification version V3.0 to enable devices with an extended address range of "A" or "B" also to perform data transmission procedures with payload data of 4 or more bits . In this process, data is exchanged in multiple cycles between the master and devices, which are in a defined relationship to each other. There are 5 combined transaction types (CTT1 – CTT5) that are defined for different applications.

The individual cycle time, with which the master and respective device exchange data with each other, depends on the number of connected devices (basic cycle) and the device profile.

As the data is transmitted in multiple consecutive cycles, its consistency can only be achieved by introducing additional measures. Information regarding the measures for consistent data transmission can be found in the documentation of the respective master.