The command issued from the PLC-CPU module or the RT-CPU module is sent via the I/O bus to the I/O control ASIC on the SRCOS module. It is transmitted to the CPU (SH7044) inside of the SERCOS module via dual port of the RAM after the command data is processed.
The module of CPU processes the command code, and writes the appropriate data into the SERCON816 or SERCOS communication ASIC, and the SERCOS communication is established with the slave devices. The module includes 128 KB of SRAM of EEPROM for saving various parameters necessary for the multi axis control.
The features of the SERCOS IF module as following:
1. SERCOS Interface
The processing time of communication was shortened by adopting the newly released SERCON616 ASIC, which can achieve a baud rate of 2, 4, 8, or 16 Mbps. This makes it possible to use the module in high axis count systems requiring fast response times.
The flash microcomputer SH 7044 made by Hitachi was selected as CPU for this module. The programs can be modified using a RS 232C connector. In addition, 256 KB of memory is available for the user’s program.
3. Load reduction of CPU module
The SERCOS interface demands a real time nature of some hundreds of u sec order from the CPU that controls the SERCOS communication. Therefore, if a real time Operating System (OS) was not available, control was not possible. SERCOS communications are controlled by exclusive use of a CPU (SH2) in the SERCOS module to overcome the limitation above.
Though the PLC tends to decline in Europe and America as the trend of the controller industry, the PLC is still a mainstream in China And Japan, and this PLC based system, which adopts the SERCOS interface, is the of its kind in the country. This system will be useful for the industries requiring the synchronization of the system and high response.