SS1102C datasheet(48/129 Pages) ETC1

48 / 129 page

Direct Sequence Spread Spectrum Baseband Modem (SSTM)

PRELIMINARY V1.8

up a burst at the end of transmission of the user’s data, “1”s will be sent automatically

(when there is no data and transmission is enabled, all “1”s will be sent).

When RXFIFO interrupt indicates that the RXshh bit is initiated, data bytes should be

read from the RXFIFO. The high level protocol should take care of the end of

transmission to avoid situation when some data can be held in the RXFIFO indefinitely

or lost on the Reset. Status bits for the overflow and underflow for the TXFIFO and

overflow for the RXFIFO are provided.

The timing relationship between the data and interrupt signals for transmit and receive

is shown in Figure 16. below. The rate with which the MCU feeds data to the transmitter

depends on the values of thresholds and burst rates.

A typical start-up of the data link is also shown in Figure 17.

In the full-duplex mode the SSTM when programmed as a Master, starts transmission as

soon as reset is released (RTS_N is enabled). As long as the Master is powered-on, the

SSTM will send out the acquisition burst and try to establish a communication link with

a remote Slave. Thus, the communication channel is occupied as soon as the Master

resets, and this can occur before any data becomes available for transmission. Once the

communication link is established, even when there is no data to be transmitted, the

Master and Slave will remain in communication with each other (sending out “1” in the

data field) indefinitely or until the Master is disabled.

Figure 16.

Full-Duplex Data Interface Timing

12.9.2

Threshold Value Calculation

The performance of the MCU should be considered when calculating TXshl and RXshh.

The time for transmission of the TXshl bytes out of the TX FIFO should be more than

the time required by the MCU to write new data into the TX FIFO. Accordingly, the

IS[2]

IS[3]

Data

READ

WRITE

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