SLAS808B – FEBRUARY 2012 – REVISED JULY 2012
The DAC34SH84 has a 32-bit LVDS bus that accepts quad, 16-bit data in word-wide format. The quad, 16-bit
data can be input to the device using a dual-bus, 16-bit interface. The bus accepts LVDS transfer rates up to 1.5
GSPS, which corresponds to a maximum data rate of 750 MSPS per data channel. The default LVDS bus input
assignment is shown in Table 3.
Table 3. LVDS Bus Input Assignment
A and B
C and D
Data is sampled by the LVDS double-data-rate (DDR) clock DATACLK. Setup and hold requirements must be
met for proper sampling. A and C data are captured on the rising edge of DATACLK. B and D data are captured
on the falling edge of DATACLK.
For both input bus modes, a sync signal, either ISTR or SYNC, is required to sync the FIFO read and/or write
The sync signal, either ISTR or SYNC, can be either a pulse or a periodic signal where the sync period
corresponds to multiples of eight samples. ISTR or SYNC is sampled by a rising edge in DATACLK. The pulse
duration t(ISTR_SYNC) must be at least equal to one-half of the DATACLK period.
The 16-bit data for channels A and B is interleaved in the form A0[15:0], B0[15:0], A1[15:0], B1[15:0], A2[15:0]…
into the DAB[15:0]P/N LVDS inputs. Similarly, data for channels C and D is interleaved into the DCD[15:0]P/N
LVDS inputs. Data into the DAC34SH84 is formatted according to the diagram shown in Figure 51, where index
0 is the data LSB and index 15 is the data MSB.
Figure 51. Data Transmission Format
The FIFO read and write pointer can also be synced by SIF SYNC as the third sync option if multi-device
synchronization is not needed. In this sync mode, the syncsel_fifoin(3:0) and syncsel_fifoout(3:0) in register
config32 need to be both set to 1000 for the SIF SYNC option.
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