Operations Manual: HPAC-100/125/150/200/250-RM SSPA
3-17
3 Operation of Stand-Alone Unit
Factory Configured DIP Switches
Some of the DIP switches are set at the factory for the configuration of the amplifier.
They should not be changed by the user. Changing these switches will result
in improper operation of the amplifier. Reference the final test data sheet supplied
with the unit for the correct factory settings in the event the factory configured DIP
switches are inadvertently changed.
Communications Protocol
The serial port protocol of the HPAC-100/125/150/200/250-RM can be configured for
RS-232 or RS-485. The microprocessor card only accepts RS-232, but by using a
converter internal to the unit, the user can communicate with RS-485. To accomplish
this, one of two marked connectors must be installed into the mating connector on the
processor card which is marked with an “S”. All connectors are labeled appropriately.
Serial Communications Format
Communications between an M&C station and a system of SSPA units is achieved
through a packet based, messaging protocol. The communication packet utilizes 8
data bits, 1 stop bit, and no parity.
Packet Format
A packet is the basic unit of information that is used to communicate between nodes on
an SSPA network. It can be thought of as a block of bytes formatted into three major
components: the header, data, and trailer. Each major component is subdivided into
fields that contain information specific to that packet. The packet format will serve for
both commands and responses. Figure 3-6 demonstrates the packet format.
Figure 3-6: Packet format and associated byte size for serial communications.
The header is divided into four fields: Frame Sync Word, Packet Length, Destination
Address, and Source Address.
Frame Sync Word: The frame sync word is a two byte field that marks the
beginning of a packet. The value placed in this field is a constant: 0xAA55.
This field provides a means for a node to synchronize to a known point in a
transmission.
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Summary of Contents for HPAC-100-RM
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