IKA SMRA + MRA, Руководство пользователя

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SMRA - SSI and BiSS
5 - SSI interface
Order codes: SMRA-BGx-…
SMRA-GGx-…
5.1 SSI (Synchronous Serial Interface)
SSI (the acronym for
Synchronous Serial Interface
)
is a synchronous point-to-point serial interface
engineered for unidirectional data transmission
between one Master and one Slave. Developed in the
first eighties, it is based on the RS-422 serial
standard. Its most peculiar feature is that data transmission is achieved by
synchronizing both the Master and the Slave devices to a common clock signal
generated by the controller; in this way the output information is clocked out at
each controller's request. Furthermore only two pairs of twisted wires are used
for data and clock signals, thus a six-wire cable is required.
The main advantages in comparison with parallel or asynchronous data
transmissions are:
•
less conductors are required for transmission;
•
less electronic components;
•
possibility of insulting the circuits galvanically by means of
optocouplers;
•
high data transmission frequency;
•
hardware interface independent from the resolution of the absolute
encoder.
Furthermore the differential transmission increases the noise immunity and
decreases the noise emissions. It allows multiplexing from several encoders, thus
process controls are more reliable with simplified line design and easier data
management.
Data transmission is carried out as follows.
At the first falling edge of the clock signal (
1
, the logic level changes from high
to low) the absolute position value is stored while at the following rising edge
(
2
) the transmission of data information begins starting from the MSB.
MAN SMRA SSI_BiSS E 1.4.odt 5 - SSI interface 18 of 40