Paradise Datacom 4 RU Chassis, Руководство по эксплуатации

Страница: 82 / 130

82 201627 REV X 4 RU SSPA Chassis Operations Manual
7.2 Serial Communication Protocol
This section describes the basic serial communication protocol between the SSPA and
host computer. The amplifier will only respond to properly formatted protocol packets.
The basic communication packet is shown in
Figure 7-4
. It consists of a Header, Data
and Trailer sub-packet.
7.2.1 Header Sub-Packet
The Header packet is divided into 3 sub-packets which are the Frame Sync, Destina-
tion Address and Source Address packets (See
Figure 7-5
).
7.2.1.1 Frame Sync Word
The Frame Sync word is a two byte field that marks the beginning of a packet. This
value is always 0xAA55. This field provides a means of designating a specific amplifier
packet from others that may exist on the same network. It also provides a mechanism
for a node to synchronize to a known point of transmission.
7.2.1.2 Destination Address
The destination address field specifies the node for which the packet is intended. It
may be an individual or broadcast address. The broadcast address is 0xFF. This is
used when a packet of information is intended for several nodes on the network. The
broadcast address can be used in a single device connection when the host needs to
determine the address of the amplifier. The amplifier will reply with its unique address.
7.2.1.3 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.
HEADER
(4 bytes)
DATA
(6-32 bytes)
Figure 7-4: Basic Communication Packet
TRAILER
(1 byte)
HEADER
(4 bytes)
DATA
(6-32 bytes)
TRAILER
(1 byte)
Frame Sync (2 bytes)
0xAA5
Destination Address
(1 byte)
Source Address
(1 byte)
Figure 7-5: Header Sub-Packet