Laird AC4490, Руководство по интеграции оборудования

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AC4490 Hardware Integration Guide
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CMD /Data
When
CMD
is held High the transceiver interprets incoming OEM Host data as transmit data to be sent to
other transceivers. When 
CMD
Data is held Low the transceiver interprets OEM Host data as command
data.
AD In
AD In can be used as a cost savings to replace Analog-to-Digital converter hardware. Reading of this pin can
be performed locally using the Read ADC command. See the
AC4490 User Guide for command descriptions.
In Range
Asserts logic Low when a client transceiver is in range of a server radio operating on the same RF Channel
and System ID. If a client cannot hear a server for the amount of time defined by Range Refresh, it will drive
In_Range
igh and enter search mode looking for a server. When a server is detected, 
In_Range
 will
always rep
In_Range
will always report Low on server transceivers.
S
ERIAL
I
NTERFACE
For the OEM host and a transceiver to communicate via serial interface they must share a serial data rate.
Refer to the following sections to ensure that the OEM host data rate matches the serial interface baud rate.
Serial Communications
The AC4490 is a TTL device which may connect to a compatible UART (Universal Asynchronous Receiver
Transmitter) or level translator to connect to serial devices. The UART mainly transmits or receives serial data.
Asynchronous Operation
Since there is no separate clock in asynchronous operation, the receiver must use a fixed baud rate and
START and STOP bits to synchronize with the transmitter.
Figure 3 shows a typical asynchronous mode signal.
Figure 3: Asynchronous Mode Signal
The UART outputs and inputs logic level signals on the TX and RX pins. The signal is high when no data is
being transmitted and low when transmission begins. The signal stays low for the duration of the START bit
and is followed by the data bits (LSB first). The STOP bit follows the last data bit and is always high. When the
STOP bit finishes, the START bit of the next transmission can occur.
Parity
A parity bit is used to provide error checking for a single bit error. When a single bit is used, parity can be
either even or odd. Even parity means that the number of ones in the data plus the parity equals an even
number and vice-versa. The ninth data bit can be used as a parity bit if the data format requires eight data
bits and a parity bit as shown in
Figure 4 .