9.4.2 TDM Mode

Time-division multiplexing (TDM) allows two or more devices to share a common DIN connection and a common DOUT connection. Using TDM mode, all devices transmit their DOUT data in user-specified sub-frames within one WCLK period. When one device transmits its DOUT information, the other devices place their DOUT terminals in a high impedance tri-state mode.

TDM mode is useable with I²S, LJF, RJF, and DSP interface modes. Refer to the respective sections for a description of how to set the TAS2555 device into those modes.

Use Register B0_P1_R3 for ASI1 and B0_P1_R23 for ASI2 to set the clock cycle offset from WCLK to the MSB. Each data bit is valid on the falling edge of the bit clock. Set Register B0_P1_R1_D[0] = 1 for ASI1 and B0_P1_R21_D[0] = 1 to force DOUT into tri-state when it is not transmitting data. This allows DOUT terminals from multiple TAS2555 devices to share a common wire to the host.

Figure 35. Timing Diagram for I²S in TDM Mode with Offset=2

For TDM mode, the number of bit-clocks per frame should be less than the programmed word-length of the data. Also the programmed offset value should be less than the number of bit-clocks per frame by at least the programmed word-length of the data.