NDC BETA LaserMike LaserSpeed Pro 8500-4, Instruction Handbook Manual

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CHAPTER
7
LaserSpeed Pro 8500-4 Instruction Handbook: SSI Communications 7-1
7 SSI Communications
Synchronous Serial Interface (SSI or Stegmann Interface) is a point to point digital communications interface
commonly used in rotary encoders. The architecture is a master (PLC or microcontroller) to slave (encoder)
where the master controls the bit-serial output of the slave shift register by generating appropriate clock sig-
nals. Electrically, the signaling interface is implemented using standard RS422/485 transceivers (refer to
standards ANSI/TIA/EIA-422-B). To synchronize the output of multiple slave devices, the master can supply
a common clock to multiple devices as long as it has a separate receiver for each slave output.
7.1 LaserSpeed Implementation
The LaserSpeed SSI implementation re-tasks the asynchronous RS422 communication interface to function
as an SSI interface. When the LaserSpeed RS422 interface is configured to function as an SSI interface, the
standard asynchronous RS422 communications is unavailable and inaccessible. The mode of operation for
the RS422 interface (standard asynchronous vs. SSI) is configurable (setup command
$S ) via the RS232 and
Ethernet TCP/UDP interfaces using LaserTrak. Once configured, the mode of operation for the RS422 inter-
face is retained (including over power-cycles) until the mode is explicitly changed by the operator/supervisor
using LaserTrak. This is an upgradeable feature to existing LaserSpeed gauges via a firmware update to the
FPGA and microcontroller. The LaserSpeed operates as an SSI slave device only.