Advertisement
ADS-14221, PPT2 User Manual
October, 2016
deadband limits. This controls the OP command mode's sensitivity to pressure change when the
'output only when pressure changes' (OP=U) option is selected.
4.3
PPT2 ADDRESSING
The PPT2 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 PPT2. The next level is
group address, which is separate from the device ID. All PPT2 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 PPT2s on a network. The device ID can be assigned by direct command or assigned
automatically based on its position from the host processor in PPT2 network. The null address (00)
is simply a default device ID that the PPT2 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
PPT2 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 PPT2s. A unit with the null address, replies with a 'null
address' header. The null address header characters are '?' for ASCII format (standard keyboard
alphanumeric characters ) or '^, &, |, or %' for binary format (fewer data bytes that are encoded for
computer translation.) 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 RS-232 units respond to global commands. Only RS-485 units with as-
signed addresses will respond to global commands. An RS-485 unit with a null address will not reply
to any global command. Global addresses are not assigned but are built into the PPT2.
18 of 85
Advertisement
