Measurement Computing PML 1000 Operating Instructions Manual page 13

PML 1000 Operating Instructions
CONFIGURING OPTIONAL SERIAL COMMUNICATION
The PML 1000 provides a RS48S/422 compatible communications interface. The interface is designed to
operate in both 2 and 4 wire (half and full duplex) communications systems. The unit supports three protocols as
standard, a simple text based command set plus MODBUS™ ASCII and RTU. (J-BUS).
PML 1000 Address [Addr]
Defines the PML 1000 address when using the PML 1000 in a multi-drop system, the range of valid addresses
is 1 - 247. The default is 1.
Baud Rate [bAud]
Allows the baud rate to be selected. The options are 1200, 2400, 4800, 9600. The default is 9600.
Protection [Prot]
Allows the PML 1000 parameter settings to be protected against change from the serial interface (write
protection ON). The default is OFF.
Parity [PrtY]
Defines parity for all communications. The options are even, odd or no parity. The default is Even.
Stop Bits [StoP]
Defines the number of stop bits, 1 or 2. The default is 1.
MODBUS™ Options
The following three parameters are for MODBUS™ communications protocols for data scaling and resolution.
Values returned from option locations i.e. Input Type, are not scaled.
Span [SPAn]
Span range used for MODBUS™ data scaling resolution.
Low Scaling Value [L¬P]
The display value which corresponds to 0 in a scaled MODBUS™ message.
High Scaling Value [H¬P]
The display value which corresponds to the SPAN (maximum) in a scaled MODBUS™ message.
Remote Terminal Unit [rtu]
If MODBUS™ RTU (sometimes known as J-BUS) protocol is required select this option ON. The default is OFF.
Transmit Delay [dELY]
Pre transmit delay adds a delay, in milliseconds, before the PML 1000 responds to any received commands.
This allows the unit to operate more reliably in two wire multidrop systems using older SCADA packages.
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