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5.3 Action Directing Commands
Action directing commands can 1) change the HPB configuration, 2) set specific parameter values, 3) activate or
deactivate controls, or 4) store information in EEPROM.
Examples of action directing commands are:
1) *00MO=P2M2 Continuous pressure readings and user message at power-up
2) *00IC=9
Set the idle count value to 9
3) *00B=09-26-00 Set B string in EEPROM to 09-26-00
A characteristic of most action directing commands is that they are preceded by a RAM, or EEPROM, write enable
(
WE
) command. This signals the HPB to write the action directing parameter(s) and is provided as a safeguard to
prevent inadvertent changes. The only exceptions to this are the initialization (
IN
) and
OP=O
commands which are
activated upon receipt.
5.4 Command Replies General
Replies are transmitted from the HPB in response to an information request inquiry or due to a power applied
condition. All replies end with a <cr> carriage return character, which can be used as a delimiter, to distinguish
between sequential responses. Replies have two forms: the
ASCII format
which consists of standard keyboard
alphanumeric characters (see Section 5.5), and the
binary format
which require fewer data bytes that are encoded
for computer translation (see Section 5.6).
The binary format replies are for pressure readings using the
P3
and
P4
commands. The replies are more compact,
require less data transmission, and more than double the data transfer capacity. However, the binary format is difficult
for people to translate and is best left for a computer to interpret.
The ASCII format characters have readable output values and do not require user interpretation. However, the binary
format will transmit a pressure reading in 6 bytes where it may take up to 16 bytes in the ASCII format. (See the Binary
Format Replies description below for a detailed explanation of the address and pressure encoding.) There is a mode
(
OP=R
) that can transmit ASCII format in 8 bytes.
When an information request command is sent to a HPB or group of HPBs the reply will take on different forms
based on the state of the HPB, the address of the HPB, or the out-of-range condition for that parameter.
A pressure-over-range error condition will occur when the applied pressure is greater than or equal to 1% of full scale
(FS) above the FS limit. For example, if the pressure applied to a 17.6 psi unit is 17.776 psi, then an over range error
condition is set (see
RS
command). Similarly, an under range condition occurs when the applied pressure is greater
than or equal to 1%FS below the minimum limit. To indicate an out-of-range condition (greater than ±1% FS), the
equal = sign will be replaced by an exclamation point ! in the pressure reading reply. This indicator will disappear
when the applied pressure is in range, but the
RS
command error flag will continue to be set until it is cleared by an
inquiry.
The maximum reading will flatten out between 1% and 5% beyond the FS limit with increasing pressure. This limit
varies from device to device but will continue to display the out-of-range indicator (! in place of =) until the
pressure drops below 1% over FS limit.