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62 208143 REV - Operations Manual, HPA3, Mini Compact Outdoor SSPA
8.1.1.3 Source Address
The source address specifies the address of the node that is sending the packet. All unique
addresses, except the broadcast address, are equal and can be assigned to individual units.
The host computer must also have a unique network address.
8.1.2 Data Packet
The data sub-packet is comprised of 6 to 32 bytes of information. It is further divided into
seven fields as shown in Figure 8-4. The first six fields comprise the command preamble
while the last field is the actual data.
8.1.2.1 Protocol ID
This field provides backward compatibility with older generation equipment protocol. It should
normally be set to zero. This field allows the unit to auto-detect other protocol versions, which
may exist in the future.
8.1.2.2 Request ID
This is an application specific field. The amplifier will echo this byte back in the response
frame without change. This byte serves as a request tracking feature.
8.1.2.3 Command
The SSPA protocol is a table based protocol. It allows the user to view and modify data tables
located on the controlled device. Throughout the remainder of this description, “sender” will
refer to the host PC, and “receiver” will refer to the SSPA unit.
Sender and receiver are limited to two commands and two command responses. The Get
Request command issued by a command sender allows monitoring of existing conditions and
parameters on the receiver. The Get Request frame should not have any bytes in the Data
Filed and be no longer than 11 bytes.
The Response frame from the receiver will contain a Get Response designator in the
Command field. If the receiver does not detect any errors in the Get Request frame, the
requested data will be attached to the response frame. The length of the Get Response frame
HEADER
(4 bytes)
DATA
(6-32 bytes)
TRAILER
(1 byte)
DATA FIELD
Protocol ID
1 Byte
Request ID
1 Byte
Command
1 Byte
Data Tag
1 Byte
Error Status /
Data Address
1 Byte
Data Length
1 Byte
Command Data
Sub Structure
0 - 26 Bytes
COMMAND PREAMBLE
Figure 8-4: Data Sub-Packet