Compared to the parallel interface, the SSI interface needs less components and the EMC-characteristics are much better. In addition less lines are needed for transmission and the possible cable length is much longer.
After the last positive-going clock-pulse edge the data line will remain for the duration of the monoflop time t3 at a low level, until the encoder is ready for a new data word. The clock line must stay high for at least as long, and then can begin a new read-out sequence again with the next falling edge.
Only for type 5850, 5870, 5862, 5882 and 9081
The updating of the data occurs synchronously with the read-out cycle. So, the data are as up-to-date as the interval time between two read-outs. A periodic read-out of the encoder in the application is therefore recommended, using appropriately short cycle times, so that current position values are constantly maintained. It is not possible to read out the same data word several times. Monoflop time of the encoder: t3 = max. 40 µs.
Only for the new Sendix Absolute encoders:
The updating of the data occurs immediately with the first falling edge of the clock signal. The data are thus always up-to-date. If a repeated read-out of the same data word is desired, then a new clock sequence must be started within the time interval t3. If the clock sequence is terminated before the necessary number of clock pulses, needed for a complete readout of the data word, has been transmitted, then after a further time interval t3 the data line will go high again and signal that the last read-out sequence has been aborted. It will also indicate that it is ready for a new data word to be sent. Monoflop time of the encoder: t3 = see data sheet.
Download Basics - Encoder