Paradise RA 5785 - Manual (Page 61)

Operations Manual, HPA3, Mini Compact Outdoor SSPA 208143 REV - 61
8.1 Serial communication
This section describes the normal communication protocol between the Mini CO SSPA and a
host computer over RS232/RS485 serial interface. Serial port settings on the host computer
must be configured for 8 bit data at no parity, with 1 stop bit. The baud rate should match the
selected baud rate parameter on the SSPA unit.
Selection between the RS232 and RS485 interface depends on the state of pin D of the J4
M&C connector. Connect pins D and d to select RS232 interface. Otherwise SSPA will
operate in RS485 mode.
The unit will only respond to properly formatted protocol packets. The basic communication
packet is shown in Figure 8-2. It consists of a Header, Data, and Trailer sub-packet.
8.1.1 Header Packet
The Header packet is divided into 3 sub-packets which are the Frame Sync, Destination Ad-
dress, and Source Address packets, as shown in Figure 8-3.
8.1.1.1 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 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.
8.1.1.2 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 or 0xAA (see Section 8.1.5
Multiple Device Access
). 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 SSPA unit will reply with
its unique address.
HEADER
(4 bytes)
DATA
(6-32 bytes)
Figure 8-2: Basic Communication Packet
TRAILER
(1 byte)
HEADER
(4 bytes)
DATA
(6-32 bytes)
TRAILER
(1 byte)
Frame Sync (2 bytes)
0xAA55
Destination Address
(1 byte)
Source Address
(1 byte)
Figure 8-3: Header Sub-Packet