DEUTSCHMANN AUTOMATION UNIGATE MB EtherCAT, Инструкция по эксплуатации

Страница: 15 / 60

17.7.17 UNIGATE
®
fieldbus gateway UNIGATE
®
MB - EtherCAT
®
V. 1.4 15
Deutschmann Automation GmbH & Co. KG SSI-interface
6 SSI-interface
The UNIGATE
®
also supports the connection of applications or products, that communicate via
SSI.
6.1 Initiation of the SSI-interface
The configuration of the SSI-interface is executed in the config mode with the WINGATE soft-
ware, Protocol SSI. The encoder type and the sampling frequency are defined via the parameter
"Resolution" (1 bit..15 bit, 24 bit...25 bit), "SSI Encoder Type" (Binary or Gray code) and "Clock
stretch".

6.1.1 Parameter sample frequency (Clock stretch)
You can change the sampling frequency. For this purpose a "Stretch value" is passed that inserts
a waiting period after each clock edge.

If a 0 is passed, there is no waiting time.

Thus the following SSI sample frequencies may vary slightly:


Waiting time = 0 → SSI-Clock ~ 333kHz (No Stretch)
Waiting time = 1 → SSI-Clock ~ 185kHz
Waiting time = 2 → SSI-Clock ~ 150kHz
Waiting time = 3 → SSI-Clock ~ 125kHz
Waiting time = 4 → SSI-Clock ~ 110kHz
Waiting time = 5 → SSI-Clock ~ 100kHz
Waiting time = 6 → SSI-Clock ~ 88kHz
Waiting time = 7 → SSI-Clock ~ 80kHz
Waiting time = 8 → SSI-Clock ~ 72kHz
Waiting time = 9 → SSI-Clock ~ 67kHz
Waiting time = A → SSI-Clock ~ 62kHz
Waiting time = B → SSI-Clock ~ 58kHz
Waiting time = C → SSI-Clock ~ 54kHz
Waiting time = D → SSI-Clock ~ 50kHz
Waiting time = E → SSI-Clock ~ 48kHz
Waiting time = F → SSI-Clock ~ 45kHz

The bit time from which these frequencies were derived, calculate as follows:

t = 3 μ s + (2* (+ 0.6µs (n* 0.6µs))), where n corresponds to the "Stretch value" (1.. F).
Without clock extension (n = 0) remains at 3 μ s → 333kHz!
The max. Bit length of 32 bits and the slowest clock this results in a total readout time of
32 * = 22
μ s ~ 700 μ s.
6.1.2 Parameter Encoder monitoring (Check Encoder)
An encoder monitoring can be activated via the parameter "Check encoder", as long as the used
SSI-encoder supports this function. After the last read encoder bit it is verified if the data line is
still at Low for at least one bit. If the UNIGATE
®
does NOT detect this bit on Low, error 12 is
issued. For example it can detect a cable break or a not connected encoder. However, it can also
be a misconfigured bit length, or a too slow read out clock.
