AeroComm Corporation LX2400 Manuel D’Utilisation
INTERFACIING TO THE LX2400
09/22/00
Preliminary
Preliminary
18
4. Interfacing to the LX2400S
4.1 OPERATING MODES
The LX2400S uses an 8-bit programmable asynchronous serial interface to communicate to a Host. The
interface uses one start bit, eight data bits, and one stop bit. Only the interface baud rate is programmable
by the Host.
interface uses one start bit, eight data bits, and one stop bit. Only the interface baud rate is programmable
by the Host.
A typical system consists of one LX2400S operating in Server Mode (LX2400S Server) communicating with
one or many LX2400S(s) operating in Client Mode (LX2400S Client). In this architecture, Clients
communicate with a single Server. Clients do not communicate with other Clients. Data transmitted by a
Server is received by all of the Clients that are in-range. The Server receives the data sent by the Client. All
protocol functions (retries, addressing, CRCs, etc.) are performed by the Host software. All frequency
hopping and synchronization is provided automatically by the LX2400S without Host intervention.
one or many LX2400S(s) operating in Client Mode (LX2400S Client). In this architecture, Clients
communicate with a single Server. Clients do not communicate with other Clients. Data transmitted by a
Server is received by all of the Clients that are in-range. The Server receives the data sent by the Client. All
protocol functions (retries, addressing, CRCs, etc.) are performed by the Host software. All frequency
hopping and synchronization is provided automatically by the LX2400S without Host intervention.
The Firmware in the LX2400S is operating in one of five modes. The Host can determine through hardware
and/or software what mode the LX2400S is operating in using the DSR pin or the software XON/XOFF data.
and/or software what mode the LX2400S is operating in using the DSR pin or the software XON/XOFF data.
4.1.1 RECEIVE MODE
The LX2400S is in RECEIVE MODE, by default, when it is not in any other operating mode. While in this
mode, the LX2400S is looking for valid preamble and sync data bytes from a transmitter. When valid
preamble and sync bytes are detected, the LX2400S will transmit data received on the RF link to the Host
using the HOST RECEIVE FRAME FORMAT. A Client LX2400S will only accept data from its Host when
it is in-range of a valid LX2400S Server.
mode, the LX2400S is looking for valid preamble and sync data bytes from a transmitter. When valid
preamble and sync bytes are detected, the LX2400S will transmit data received on the RF link to the Host
using the HOST RECEIVE FRAME FORMAT. A Client LX2400S will only accept data from its Host when
it is in-range of a valid LX2400S Server.
4.1.2 TRANSMIT MODE
The Host software initiates transmission of a data packet on the RF link by lowering TE, waiting for CTS to
go low, followed by sending the specified preambles bytes, sync byte, data length, and data. Both maximum
data byte gaps and packet times must be adhered to. At the end of the transmission TE must return to a
Logic Level High. After TE is taken high by the Host, the LX2400S will drive CTS high. This indicates the
LX2400S is returning to RECEIVE MODE. The Host software must perform MAC layer functions (retries,
addressing CRCs, etc.). If the Client LX2400S is not in-range of a LX2400S Server, TRANSMIT MODE
will not be entered. The Client LX2400S will not respond with CTS.
go low, followed by sending the specified preambles bytes, sync byte, data length, and data. Both maximum
data byte gaps and packet times must be adhered to. At the end of the transmission TE must return to a
Logic Level High. After TE is taken high by the Host, the LX2400S will drive CTS high. This indicates the
LX2400S is returning to RECEIVE MODE. The Host software must perform MAC layer functions (retries,
addressing CRCs, etc.). If the Client LX2400S is not in-range of a LX2400S Server, TRANSMIT MODE
will not be entered. The Client LX2400S will not respond with CTS.
The following sequence transmits a packet on the RF link:
1. The Host drives the TE pin low.
2. The LX2400S responds by driving CTS low.
3. The Host sends serial bytes as specified in the HOST TRANSMIT FRAME FORMAT. The
2. The LX2400S responds by driving CTS low.
3. The Host sends serial bytes as specified in the HOST TRANSMIT FRAME FORMAT. The
LX2400S transmits the HOST TRANSMIT FRAME FORMAT on the RF link as it receives each
byte from the Host.
byte from the Host.
4. The Host drives TE high after the last byte is received by the LX2400S.
5. The LX2400S responds by driving CTS high and returns to RECEIVE MODE.
5. The LX2400S responds by driving CTS high and returns to RECEIVE MODE.