JAJSFT4C August 2018 – June 2019 ADS9224R , ADS9234R
PRODUCTION DATA.
In clock re-timer (CRT) protocols, the device sends out data on the SDO lines with a synchronized clock on the STROBE line. The data are synchronized to the rising edges of the STROBE pulses. For CRT protocols with a single data rate, the host can capture data on the falling edges of the STROBE pulses. For double data rate, the host must capture data on both edges of STROBE. The clock source for the STROBE output can be selected as an external clock (SCLK) or an internal clock by configuring the CRT_CLK_SELECT bits in the CRT_CFG register. For reading data from the device, SCLK is only required when the STROBE output is selected as an external clock. The SDOs that are not enabled by the BUS_WIDTH register are set to tri-state. Table 6 provides the details of different CRT protocols to read data from the device.
PROTOCOL(1) | SCLK POLARITY(2) | CAPTURE EDGE | MSB LAUNCH EDGE | BUS WIDTH(4) | tREAD(3) | TIMING DIAGRAM |
---|---|---|---|---|---|---|
CRT-S-SDR | Low (CPOL = 0) | STROBE falling | 1st STROBE rising | 1 | [15.5 × tSTROBE + m] | Figure 56 |
CRT-D-SDR | Low (CPOL = 0) | STROBE falling | 1st STROBE rising | 2 | [7.5 × tSTROBE + m] | Figure 58 |
CRT-Q-SDR | Low (CPOL = 0) | STROBE falling | 1st STROBE rising | 4 | [3.5 × tSTROBE + m] | Figure 60 |
CRT-S-DDR | Low (CPOL = 0) | STROBE rising and falling | 1st STROBE rising | 1 | [7.5 × tSTROBE + m] | Figure 57 |
CRT-D-DDR | Low (CPOL = 0) | STROBE rising and falling | 1st STROBE rising | 2 | [3.5× tSTROBE + m] | Figure 59 |
CRT-Q-DDR | Low (CPOL = 0) | STROBE rising and falling | 1st STROBE rising | 4 | [1.5 × tSTROBE + m] | Figure 61 |
Figure 56 through Figure 61 illustrate timing diagrams for the CRT-S-SDR, CRT-S-DDR, CRT-D-SDR, CRT-D-DDR, CRT-Q-SDR, and CRT-Q-DDR protocols, respectively.
For reading data, SCLK is only required when the STROBE output is selected as SCLK (external clock) in the CRT_CFG register. However, for configuring registers, SCLK is always required.