Data Sheet

AC4490

Datasheet

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5.2.11 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 high and enter search

mode looking for a server. When a server is detected, In_Range will always report Low on server transceivers.

6 SERIAL INTERFACE

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.

6.1 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.

6.2 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.

6.3 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.

Figure 4: Even Parity Bit

Note: Enabling parity cuts throughput and the interference buffer in half.

Table 5 displays supported asynchronous serial data formats:

Table 5: Supported Serial Formats

Data Bits

Parity

Stop Bits

Transceiver Programming Requirements

Parity Disabled