6-13 Communications
Data Organization
This section describes the internal data structure of PLuS controllers, and how this data
may be accessed via serial communications. The data has been organized as a series
of "Coils" and "Registers" compatible with PLC programming techniques. You access
and/or change the data within a PLuS controller by forcing coils ON or OFF, and by
reading and writing register data.
A PLuS Controller can be completely programmed via the serial interface. All controller
data, such as pulses, speed compensation, timed output values, etc., are available as
registers. Configuration data, such as the direction of rotation, number of keyboards,
number of analog outputs, etc., is also available as register data. The controller is
programmed by writing to these registers. Data is monitored within the controller by
reading from these registers.
Note: The ability of the EEPROM to retain data is reduced after 100,000 write cycles.
Do not set up routines that constantly write data to the EEPROM's.
Mapping
In addition to accessing controller data via dedicated registers, specific indexed data
items can be accessed through the 240 data display registers. This is done by "map-
ping" a specific indexed data element to a data display register; a data display register is
assigned to represent a pulse, speed comp value, etc. Once an indexed data element
is mapped it can be accessed either through the data display register or through the
dedicated register.
Mapping is useful when displaying more than one instance of an indexed data element
at once. For instance, speed compensation is accessed via three registers; 1) a channel
index, 2) a leading edge value, and 3) a trailing edge value. This means that the values
of speed compensation for all channels can be accessed, but only one at a time. To
display more than one value of speed compensation at once, simply map the values
to a series of data display registers.
You must define how many mappings are available through the Map Limit register.
Modbus
Modbus ASCII protocol is used for serial communications.
Set host controller communication parameters to 7 data bits, 2 stop bits, no parity.
Limit the number of consecutive registers or coils read to 32.
Serial Communications Using Modbus ASCII Protocol (PS-6144-MB Units)
Содержание Plus PS-6144 Series
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