SP2-433-160 Datasheet, PDF (3/27 Pages) Radiometrix Ltd – UHF SpacePort Transceiver

1. FUNCTIONAL DESCRIPTION
On receipt of a packet downloaded by the Host, the FSP2 will append to the packet: Preamble, start
byte and a error check code. The packet is then coded for security and mark:space balance and
transmitted through the BiM2 Transceiver as a 160kbps synchronous stream. One of four methods of
collision avoidance (listen before TX) may be user selected.
When not in transmit mode, the SP2 continuously searches the radio noise for valid preamble. On
detection of preamble, the SP2 synchronises to the in-coming data stream, decodes the data and
validates the check sum. The Host is then signalled that a valid packet is waiting to be unloaded. The
format of the packet is entirely of the users determination except the 1st byte (the Control Byte) which
must specify the packet type (control or data) and the packet size. A valid received packet is presented
back to the host in exactly the same form as it was given.
To preserve versatility, the SP2 does not generate routing information (i.e.
source/ destination addresses) nor does it handshake packets. These network
specific functions should be performed by the host.
Additional features of the SP2 include extensive diagnostic/debug functions for evaluation and
debugging of the radio and host driver software, a built in self test function and a sleep mode / wake-up
mechanism which may be programmed to reduce the average current to less than 100µA. The operating
parameters are fully programmable by the host and held in EEPROM, the host may also use the
EEPROM as a general purpose non-volatile store for addresses , routing information etc.
1.1 OPERATING STATES
The SP2 has four normal operating states:
• IDLE / SLEEP
• HOST TRANSFER
• TRANSMIT
• RECEIVE
IDLE/SLEEP
The IDLE state is the quiescent/rest state of the SP2. In IDLE the SP2 enables the receiver and
continuously searches the radio noise for message preamble. If the power saving modes have
been enabled the SP2 will pulse the receiver on, check for preamble and go back to SLEEP if
nothing is found. The 'ON' time is 2.5ms, OFF time is programmable in the SP2’s EEPROM and
can vary between 22ms and 181ms. The TX Request line from the Host is constantly monitored
and will be acted upon if found active (low). A TX Request will immediately wake the SP2 up
from SLEEP mode.
HOST TRANSFERS
If the host sets the TX Request line low a data transfer from the Host to the SP2 will be
initiated. Similarly the SP2 will pull RX Request low when it requires to transfer data to the
Host (this may polled or used to generate a Host interrupt).
The transfer protocol is fully asynchronous, i.e. the host may service another interrupt and then
continue with the SP2 transfer. It is desirable that all transfers are completed quickly since the
radio transceiver is disabled until the Host <> SP2 transfer is completed. Typically a fast host
can transfer a 60 byte packet to / from the SP2 in under 1ms.
Radiometrix Ltd, SP2 data sheet
page 3