AD1928

Rev. 0 | Page 19 of 32

DAISY-CHAIN MODE

The AD1928 also allows a daisy-chain configuration to expand

the system to 4 ADCs and 16 DACs (see Figure 18). In this mode,

TDM data stream belong to the first AD1928 in the chain and

the last eight slots belong to the second AD1928. The second

AD1928 is the device attached to the DSP TDM port.

To accommodate 16 channels at a 96 kHz sample rate, the

AD1928 can be configured into a dual-line TDM mode, as

shown in Figure 19. This mode allows a slower DBCLK than

normally required by the one-line TDM mode.

Again, the first four channels of each TDM input belong to the

first AD1928 in the chain and the last four channels belong to

the second AD1928.

The dual-line TDM mode can also be used to send data at a

192 kHz sample rate into the AD1928, as shown in Figure 20.

There are two configurations for the ADC port to work in

shown in Figure 21. The second configuration is shown in

channels occupy the first eight slots; the second eight slots are

empty. The TDM_IN of the first AD1928 must be grounded in

all modes of operation.

The input/output pins of the serial ports are defined according

to the serial mode selected. See Table 13 for a detailed

description of the function of each pin. See Figure 26 for a

typical AD1928 configuration with two external stereo DACs

and two external stereo ADCs.

Figure 23 through Figure 25 show the serial mode formats. For

maximum flexibility, the polarity of LRCLK and BCLK are

programmable. In these figures, all of the clocks are shown with

DLRCLK

DBCLK

8 DAC CHANNELS OF THE FIRST IC IN THE CHAIN

8 UNUSED SLOTS

8 DAC CHANNELS OF THE SECOND IC IN THE CHAIN

MSB

DSDATA1 (TDM_IN)

OF THE SECOND AD1928

DSDATA2 (TDM_OUT)

OF THE SECOND AD1928

THIS IS THE TDM

TO THE FIRST AD1928

DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4 DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4

DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4

32 BITS

DSP

SECOND

AD1928

FIRST

AD1928

Figure 18. Single-Line DAC TDM Daisy-Chain Mode (Applicable to 48 kHz Sample Rate, 16-Channel, Two-AD1928 Daisy Chain)