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COMMUNICATION INTRODUCTION
The DXD Digital Pressure Transducer uses a simple ASCII
character based string transmission for communications. A
DXD Unit cannot initiate this communication
process. A “HOST DEVICE”, i.e. a computer or terminal
device must be used to initiate communications by querying
the DXD Unit.
If multiple DXD Units are on the same communication bus
then each Unit must have a unique, 2-digit address between
00 and 99. Only a single DXD Unit can be communicated
with at any one time, therefore,with multiple units on the
communication bus each unit must have a means of being
identified uniquely. The unique address is the means by
which the HOST DEVICE addresses each unit.
For the special case where only one DXD Unit is on the com-
munications bus, wildcard characters “**” can be used to
address that single unit.
WARNING: Special care should be taken when using wild-
card addressing for communications. To minimize problems
that may arise from its use, we suggest only using wildcard
addressing for testing and troubleshooting purposes.
Commands issued to a DXD Unit can be classified as one of
two types.
1. Read Commands: These always return a value
Write Commands: In the ack/nak mode an ack or nak + CR
LF will always be returned. In the A/N error mode an A or N
+ CR LF will always be returned. In “Legacy” mode nothing
will be returned except in the case of the “ew” command.
COMMUNICATIONS SETTINGS
The DXD Transducer uses the following communications
settings:
Bits Per Second Rates:
1200, 2400, 4800, 9600, 19200,
38400, 57600, 115200
Data Bits:
7
Stop Bits:
1
Parity:
Even
Flow Control:
None
COMMUNICATIONS PROTOCOL
Each command is initiated with a pound sign (#).
Following the pound sign, is the 2-character DXD Unit
address.
The address is followed by a 2-character alpha command
mnemonic representing the command being issued. For write
commands, following the command mnemonic there is usu-
ally an input value to set. Finally the termination character, a
carriage return, is used to terminate the command.
Start Character
#
DXD Address
01 through 99
Command Mnemonic
2 Character Alpha
Input Value
Alpha or Numeric CR
Termination Character
CR
Ex. Read Command #02PS<CR>, this command is directed
to DXD Unit address ‘02’, and a PSI pressure reading is being
requested.
Ex. Write Command #01ulUNIT 100<CR>, this command is
directed to DXD Unit address ‘01’ and its user label is being
set to UNIT 100.