STA680 datasheet(29/48 Pages) STMICROELECTRONICS

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STA680

Digital I/O and memory interfaces

5.2

Base-band I2S interface

The STA680 has two digital Base-Band Interfaces (BBI1 and BBI2).

The tuner receives the analog signal from the antenna, samples it, performs down

conversion and channel selection, and transmits the digital base-band stream to the

STA680 by means of BB1 and BB2.

Each BB interface consists of maximum four wires: up to two serial data lines I/Q (or one

single data lines where I and Q data are multiplexed), one bit clock line and one frame clock

line. The serial data is always transmitted with the MSB first and a 16-bit word length. The

complex base-band signal needs to be at zero IF.

Most common data rates are supported by using the internal base-band sample rate

converter. The allowed base-band interface data rates are:



650 kS/s,



675 kS/s,



744.1875 kS/s



912 kS/s.

Table 6. describes the pin functionality of both BBI1 and BBI2.

The base-band interface supports the modes shown in Figure 9 Timing information for the

protocols shown in Figure 9 is detailed in Table 7.

Table 6. Baseband interfaces pin list

Pin name

Designation

Type

BB1_WS

Primary baseband interface word strobe

BB1_BCK

Primary baseband interface bit clock

BB1_I

Primary baseband interface serial I data (or Primary baseband

data I/Q multiplexed)

BB1_Q

Primary baseband interface serial Q data

BB2_WS

Secondary baseband interface word strobe

BB2_BCK

Secondary baseband interface bit clock

BB2_I

Secondary baseband interface serial I data (or Secondary

baseband data I/Q multiplexed)

BB2_Q

Secondary baseband interface serial Q data

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