SP2-433-160 Datasheet, PDF (9/27 Pages) Radiometrix Ltd – UHF SpacePort Transceiver

2.3.2 SENDING AND RECEIVING DATA PACKETS
Data packets are sent to / received from remote SP2’s. They begin with a control byte with bit 7 cleared
and may be of variable length and contain up to 60 bytes of user determined data.
PT WU0 BC5 BC4 BC3 BC2 BC1 BC0
7
6
5
4
3
2
1
0
BC5 - BC0 - 6 Bit Byte Count
6 Bit byte count (includes itself), byte count must
be in the range 1 to 61 (01 to 3D HEX)
PT - Packet Type
0 = Data Packet
WU0 - Preamble Control
WU0 Function
0 Normal preamble
EEPROM Parameter
location 01H determines time
1 Power save wake-up location 02H determines time
figure 8: Control byte for data packet
The remainder of the bytes in the data packet are of the users determination.
The packet would usually be made up of a number of fields consisting of some
but not necessarily all of the following :-
Source address / ID
Destination address / ID
System ID
Packet count
Encryption / Scrambler control
Additional error check codes ( The SP2 performs it's own error checks)
Routing information ( for repeaters)
Link control codes (connect/disconnect/ACK/NAK etc.)
Data field
2.3.3 SP2 MEMORY ACCESS
The SP2’s EEPROM memory can be accessed by setting bit 7 in the control byte. Bit 6 (R/W flag) defines
a memory read or write. The bits left define the address.
Read from memory
1 0 Address (6 bit) _{Control Byte}
76
0
SP2
Write to memory
Data Byte
1 1 Address (6 bit) _{Control Byte}
76
0
SP2
Data byte
1⁷ 0 Address (6 bit)⁰
76
0
figure 9: SP2 memory access
Radiometrix Ltd, SP2 data sheet
page 9