
22
5.0 COMMANDS
5.1 Command Format
Communication between the host or control processor and a HPB is accomplished by message transfers, or
commands and replies. Communications initiated by the host processor to one or more HPBs are called
commands
and must begin with an * or a ~
header character
. All commands must be terminated by a <cr> (carriage return or
ENTER key). Communications initiated by a HPB to the host are called responses or
replies
, and begin with one of
ten unique header characters (2 for ASCII, 8 for binary) and are also terminated with a <cr>.
Commands may either
request information
from one or more HPBs such as read pressure, or
direct action
to one or
more HPBs such as change a configuration value or operating mode.
Typical HPB command format: *ddcc = nnn
<cr>
Where: *
is the command header character
dd
is the decimal address of the command message (00-99)
cc
is the command code. The command code characters can be one letter, two letters, or a letter
and a number. The letters are not case sensitive; i.e., either an upper case or lower case may
be used. The HPB will convert the character to upper case.
=
equal sign (required in some commands)
nnn
additional characters (required in some commands)
<cr>
carriage return (do not type, press the ENTER key)
Note:
For multi-drop mode, alternate headers are available. (see
MO
command)
For Ring mode, when manually applying commands to one or more HPBs which are in the continuous send mode (
P2
,
P4
,
T2
,
T4
), the special header character $ should be used to suspend all HPB transmissions while the command
message is being typed. The $ is immediately followed by the normal command format.
Also for ring mode, if an erroneous command is sent to the HPB, it is echoed back to the host in the same form it was
sent. The only exception to this is when a group or global address command (ID = 90 to 99) is sent such as
*99S2=15<cr>. These addresses will always echo the command back to the host processor after being read by all
HPBs.
Commands are not executed until the carriage return is applied; therefore, any command message may be re-entered
at any time prior to the carriage return. To do this, type a * followed by the command, or press a carriage return and
retype the command.
Only the minimum number of characters is required for command inputs to distinguish between various command
options. For example,
DU=HP, DU=HPA
, or
DU=HPAXYZ
will all set the display units to hectopascals, since only the
first two characters (
HP
) are needed. Also, when a parameter value is entered that exceeds the stated range for that
value, the parameter will be set to the maximum value for that range.
5.2 Information Request Commands
Information request commands retrieve information from the HPB as an inquiry. One example would be an idle count
command inquiry. The command
*00IC
would request the idle count value. The response may be
?01IC=213
,
assuming the unit had not been assigned a device ID. A characteristic of the information request command is that the
=nnn
portion of the command format is dropped.
Most commands that set parameters may be used in this form to inquire about that parameters value. For commands
that have a single letter command code (
cc
), use that letter followed by an = equal sign to form an inquiry. For
example, to inquire about the serial number, use
*00S=
as an information request.