B&B Electronics Zlinx Xtreme ZXT9-RM, Руководство пользователя

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Document Number: ZXTxRM-5110m
Page
60
6.3 RF Modem Operation
6.3.1 Transport Operation
By default, modem operates in Transparent Mode. When operating in this mode, the
modems act as a serial line replacement - all received UART data is queued up for RF
transmission. When RF data is received, the data is sent out of the modem.
6.3.2 Serial to RF Packetization
Data is buffered in the input buffer until one of the following causes the data to be
packetized and transmitted:
•
No serial characters are received for the amount of time determined by the RO
(Packetization Timeout) parameter. If RO = 0 packetization begins when a character is
received.
•
The maximum number of characters that will fit in an RF packet (2048 for ZXT9-RM) (202
for ZXT24-RM) is received.
•
The Command Mode Sequence (GT + CC + GT) is received. Any character buffered in
the input buffer before the sequence is transmitted.
If the modem cannot immediately transmit (for instance, if it is already receiving RF data),
the serial data is stored in the input buffer. The data is packetized and sent at any RO
timeout or when the maximum packet size is received.
If the input buffer becomes full, hardware or software flow control must be implemented in
order to prevent overflow (loss of data between the host and modem).
6.3.3 API Operation
API (Application Programming Interface) Operation is an alternative to the default
Transparent Operation. The frame-based API extends the level to which a host application
can interact with the networking capabilities of the modem.
When in API mode, all data entering and leaving the modem is contained in frames that
define operations or events within the modem.
Transmit Data Frames (received by modem) include:
•
RF Transmit Data Frame
•
Command Frame (equivalent to AT commands)
Receive Data Frames (sent out by modem) include:
•
RF-received data frame
•
Command response
•
Event notifications such as reset, associate, disassociate, etc.
The API provides alternative means of configuring modems and routing data at the host
application layer. A host application can send data frames to the modem that contain
address and payload information instead of using command mode to modify addresses.
The modem will send data frames to the application containing status packets; as well as
source, RSSI and payload information from received data packets.