Figure 4.12-Hpb Rs-232 Ring Network - Honeywell HPB User Manual

HPB\HPA User Manual
4.7 HPB ADDRESSING
The HPB provides three levels of addressing. The lowest level of address is the individual unit address, or
device ID. This address level is used to address any single HPB. The next level is group address, which is
separate from the device ID. All HPB units with the same group address will respond to a command sent to
this level address. The last is a global address, which is read by all HPB's on the network. The device ID
can be assigned by direct command or assigned automatically based on its position from the host processor
in HPB network. The null address (00) is simply a default device ID that the HPB automatically assumes
until one is assigned. That is, upon power-up, if there is no ID assigned, and an ID has not been stored in the
EEPROM, then the HPB will assign itself the ―00‖ null address.
The individual unit address, or device ID, has an assigned range from 01-89. The null address 00 is the
factory default address for unassigned HPB's. A unit with the null address, replies with a ‗null address'
header. The null address header characters are ‗?' for ASCII format or ‗^, &, |, or %' for binary format (see
Section 5.5 for these format types). A unique device ID allows the host processor to send commands to
specific units on a bus.
The second level of addressing is a multicast, or group, address in the range of 90-98. Each unit can be
assigned a group address by the ID command. A unit responds to its group address in the same manner as it
does to its global address described below. The group addressing allows the host processor to send
commands to several units having the same group address. The factory default group address is 90.
The highest level of addressing is the broadcast, or global, address 99. All units receive global addressed
commands. All ring networked units respond to global commands. Only multi-drop units with assigned
addresses will respond to global commands. A multi-drop unit with a null address will not reply to any global
command. The global address is not assigned but is built into the HPB.
RS-232 Ring Network
The RS-232 network consists of a three-wire bus (TD, RD, and GD) that begins and ends at the host
processor. The RS-232 electrical standard requires that the distance between units not exceed 60 feet (18
meters). An advantage of the RS-232 network is that it interfaces directly to the serial COM port of most
personal computers. The maximum number of HPBs with assigned device IDs on a network is 89.
An HPB ring network connection of six units is shown in Figure 4.12. In this example, the Device IDs are
sequential, starting from 01, from the transmit port of the host processor around the loop. There are two
address groups, 91 and 93; each have 3 HPB units assigned.
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Figure 4.12-HPB RS-232 Ring Network

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