Watlow MICRODIN - Manual (Page 15)

Wa t l o w M i c r o D I N 2 . 5
Communications
Setup
MicroDIN, A Modbus ™ Remote Terminal Unit (RTU)
RTU
The MicroDIN uses Modbus ™ RTU (remote terminal unit) protocol to read and
write to registers that can be viewed or changed from a personal computer.
Sending ASCII text commands to the MicroDIN will not work.
Access Via Registers
Each MicroDIN parameter has a corresponding Modbus ™ register and access
privileges. The value of each parameter is stored in a Modbus ™ register. The
access privilege — read only, write only or read/write — determines whether you
can change and/or view a parameter’s value.
Chapter 5 explains some of the
interactions between parameters. The tables at the end of this chapter show the
parameters and their setup order.
MicroDIN Supports...
Multiple Register Reads
MicroDIN supports Modbus ™ Commands 03 and 04 read of a 1- to 32-register
block. Responses from -1999 to 9999 are valid data for up to 32 register writes.
Modbus ™ 32000 Errors
A Modbus ™ read command response of -32000 indicates that a register is not
implemented; -32001, register not active; or -32002, not read accessible.
Single Register Writes
MicroDIN supports a Modbus ™ write command (06) to a single register.
Multiple Register Writes
MicroDIN supports a Modbus ™ write command (16) for multiple writes as long
as the data length is 1.
Writing to address 0 broadcasts to all devices on the network.
Write Exceptions
MicroDIN supports write exceptions: 01, illegal function; 02, illegal register; 03,
illegal data.
Loop Back
MicroDIN supports a Modbus ™ write command 08, “loop back” to echo a
message.
Compatible Software
You will need compatible software to interact with a MicroDIN controller. One
such program is included with the MicroDIN Startup Kit. If you are accustomed
to using a Modbus
™ , see the Appendix for information to help write your own
Modbus ™ software application.
ç
CAUTION:
Avoid writing
continuously to
EEPROM memory.
Continuous writes
may result in
premature control
failure, system
downtime and
damage to
processes and
equipment.
See Disable Non-
volatile Memory
(System Group),
Ch. 5.