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STA020D Datasheet(PDF) 5 Page - STMicroelectronics |
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STA020D Datasheet(HTML) 5 Page - STMicroelectronics |
5 / 11 page GENERAL DESCRIPTION The STA020D is a monolithic CMOS circuit that encodes and transmits audio and digital data ac- cording to the AES/EBU, IEC 958, S/PDIF, and EIAJ CP-340 interface standards. The chip ac- cepts audio and control data separately; multiplex and biphase-mark encode the data internally and drive it, directly or through a transformer, to a transmission line. The STA020D has dedicated pins for the most important control bits and a serial input port for the C, U and V bits. Line Drivers The differential line drivers for STA020D are low skew, low impedance, differential outputs capable of driving 110Ohm transmission lines. (RS422 line driver compatible). They can also be disabled by resetting the device (RST = low). STA020D DESCRIPTION The STA020D accepts 16 to 24-bit audio sam- ples through a serial port configured in one of seven formats; provides several pins dedicated to particular channel status bits and allows all chan- nel status, user and validity bits to be serially in- put through port pins. This data is multiplexed, the parity bit is generated and the bit stream is biphase-mark encoded and driven through an RS422 line driver. The STA020D operates as a professional or con- sumer interface transmitter selectable by pin 2, PRO. As a professional interface device, the dedicated channel status input pins are defined according to the professional standard, and the CRC code (C.S. byte 23) can be internally gener- ated. As a consumer device, the dedicated channel status input pins are defined according to the consumer standard. A submode provided under the consumer mode is compact disk, CD, mode. When transmitting data from a compact disk, the CD subcode port can accept CD subcode data, extract channel status information from it, and transmit it as user data. The master clock , MCK, controls timing for the entire chip and must be 128xFs. As an example, if stereo data is input to the STA020D at 44.1kHz, MCK input must be 128 times that or 5.6448MHz. Audio Serial Port The audio serial port is used to enter audio data and consists of three pins: SCK, SDATA and FSYNC, SCK clocks in SDATA, which is double buffered, while FSYNC delineates the audio sam- ples and may indicate the particular channel, left or right. To support many different interfaces, M2, M1 and M0 select one of seven different formats for the serial port. The coding is shown in Table 3 while the formats are shown in Figure 3. Format 0 and 1 are designed to interface with Crystal ADCs. Format 2 communicates with Mo- torola and TI DSPs. Format 3 is reserved. Format 4 is compatible with the I 2S standard. Formats 5 and 6 make the STA020D look similar to existing 16- and 18-bit DACs and interpolation filters. For- mat 7 is an MSB-last format and is conducive to serial arithmetic. SCK and FSYNC are outputs in Format 0 and inputs in all other formats. In For- mat 2, the rising edge of FSYNC delineates sam- ples and the falling edge must occur a minimum of one bit period before or after the rising edge. In all formats except 2, FSYNC contains left/right information requiring both edges of FSYNC to de- lineate samples. Formats 5 and 6 require a mini- mum of 16- or 18-bit audio words respectively. In all formats other than 5 and 6, the STA020D can accept any word length from 16 to 24 bits by add- ing leading zeros in format 7 and trailing zeros in the other formats, or by restricting the number of SCK periods between active edges of FSYNC to the sample word length. FSYNC must be derived from MCK, either through a DSP using the same clock or using counters. If SFYNC moves (jitters) with respect to MCK by four MCK periods, the internal counters and CBL may be reset. Table 1. Audio Port Modes M2 M1 M0 Format 0 0 0 0 - FSYNC & SCK Output 0 0 1 1 - Left/Right, 16-24 Bits 0 1 0 2 - Word Sync, 16-24 Bits 0 1 1 3 - Reserved 1 0 0 4 - Left/Right, I 2S Compatible 1 0 1 5 - LSB Justified, 16 Bits 1 1 0 6 - LSB Justified, 18 Bits 1 1 1 7 - MSB Last, 16-24 Bits STA020D 5/11 |
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