AMM80 • SSI, BiSS, & RS-485
5 - SSI interface
Order code:
AMM80xx/xxxBG1-...
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 AMM80 SSI_BiSS_RS485 E 1.5.odt
5 - SSI interface
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