
27
When several HPB units are serially connected as a network, the reply sequence now depends on the type of
address (individual, group, or global) and command type (sequential response or not). Refer to Table 4 Command
Summary Table, for the sequential response type of each command.
Different types of command and reply messages are shown in Figure 13 for a three-HPB network connected to a host
processor. The commands are sent to individual units, groups and global addresses. Note that for group and global
addressed commands, the command is sent around the network and returns to the host processor. If the host
processor sends a sequential response command to a group or global address, then the reply(ies) may return before
or after the command, depending on the command type. Examples of the different types of sequential response
commands are also shown. The reply format is ASCII.
5.7 Command And Reply Sequencing
The HPB can be operated in either a multi-drop or ring configuration. See Section 6 for various electrical connections.
In these modes, the host processor sends a command and the HPB responds with a reply. The reply and timing of the
reply are dependent on the command and HPB network configuration.
Typical command and reply messages are shown in Figure 12 for a single HPB connected to a host processor. The
CMD
waveform represents the command sent from the host to the HPB. It is actually a sequence of TTL level ASCII
characters sent at the correct baud rate and parity type (see
BP
command). The
REPLY
is the corresponding
response from the HPB to the CMD command. Note that the command input is case insensitive, that is, either upper
case or lower case letters may be used.
Computer
or Host
Processor
T - Transmit
R - Receive
ID=01
Group=90
REPLY
CMD
T
R
R
T
HPB
COMMAND
REPLY
COMMENT
Power-on
?01HPA___17.6_PSIa
Factory set power-on message (16 character)
*01S=
?01S=00036714
Read factory set serial number
*99we
*99WE
RAM or EEPROM write enable (global)
*99id=01
*99ID=02
Set device IDs (global)
*01P1
#01CP=12.345
Read pressure from device ID=01
*01ID
#01ID=90
Read group number
Figure 12. Single HPB Command and Reply