Справочник Пользователя для AeroComm Corporation 4424200
3/23/2006
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5. Theory of Operation
5.1 H
ARDWARE INTERFACE
Below is a description of all hardware pins used to control the LT4424.
5.1.1 TXD (Transmit Data) and RXD (Receive Data) (pins 2 and 3 respectively)
The LT4424 accepts 5V TTL level asynchronous serial data in the RXD pin and interprets that data as
either Command Data or Transmit Data. Data is sent from the transceiver to the OEM Host via the TXD
pin. The data must be of the format 8-N-1 (8 data bits, No Parity bits, One stop bit).
either Command Data or Transmit Data. Data is sent from the transceiver to the OEM Host via the TXD
pin. The data must be of the format 8-N-1 (8 data bits, No Parity bits, One stop bit).
5.1.2 Hop Frame (pin 6)
The LT4424 is a frequency hopping spread spectrum radio. Frequency hopping allows the system to
hop around interference in order to provide a better wireless link. Hop Frame transitions logic Low at
the start of a hop and transitions logic High at the completion of a hop. The OEM Host is not required
to monitor Hop Frame.
hop around interference in order to provide a better wireless link. Hop Frame transitions logic Low at
the start of a hop and transitions logic High at the completion of a hop. The OEM Host is not required
to monitor Hop Frame.
5.1.3 CTS Handshaking (pin 7)
The LT4424 has an interface buffer size of 256 bytes. If the buffer fills up and more bytes are sent to
the transceiver before the buffer can be emptied, data corruption will occur. The transceiver prevents
this corruption by asserting CTS High as the buffer fills up and taking CTS Low as the buffer is
emptied. CTS On in conjunction with CTS On Hysteresis control the operation of CTS. CTS On
specifies the amount of bytes that must be in the buffer for CTS to be disabled (High). Even while CTS
is disabled, the OEM Host can still send data to the transceiver, but it should do so carefully. Once
CTS is disabled, it will remain disabled until the buffer is reduced to the size specified by CTS On
Hysteresis. The following equation should always be used for setting CTS On, CTS On Hysteresis and
RF Packet Size:
the transceiver before the buffer can be emptied, data corruption will occur. The transceiver prevents
this corruption by asserting CTS High as the buffer fills up and taking CTS Low as the buffer is
emptied. CTS On in conjunction with CTS On Hysteresis control the operation of CTS. CTS On
specifies the amount of bytes that must be in the buffer for CTS to be disabled (High). Even while CTS
is disabled, the OEM Host can still send data to the transceiver, but it should do so carefully. Once
CTS is disabled, it will remain disabled until the buffer is reduced to the size specified by CTS On
Hysteresis. The following equation should always be used for setting CTS On, CTS On Hysteresis and
RF Packet Size:
CTS On – CTS On Hysteresis = RF Packet Size
5.1.4 RTS Handshaking (pin 8)
With RTS Mode disabled, the transceiver will send any received packet to the OEM Host as soon as
the packet is received. However, some OEM Hosts are not able to accept data from the transceiver all
of the time. With RTS Mode Enabled, the OEM Host can keep the transceiver from sending it a packet
by disabling RTS (logic High). Once RTS is enabled (logic Low), the transceiver can send packets to
the OEM Host as they are received. Note: Leaving RTS disabled for too long can cause data loss
once the transceiver’s receive buffer fills up.
the packet is received. However, some OEM Hosts are not able to accept data from the transceiver all
of the time. With RTS Mode Enabled, the OEM Host can keep the transceiver from sending it a packet
by disabling RTS (logic High). Once RTS is enabled (logic Low), the transceiver can send packets to
the OEM Host as they are received. Note: Leaving RTS disabled for too long can cause data loss
once the transceiver’s receive buffer fills up.