SPI Port Modes
The SPI port can be used in either of two modes, Burst Mode,
or Continuous CCLK Mode, as described below:
Continuous CCLK Mode
In this mode, the maximum CCLK frequency is 3 MHz. The
CCLK can run continuously between transactions. Please note
that the Low-to-Hi transition of the CLATCH with respect to
the rising edge of CCLK must be at least 130 ns, as shown in
Figure 7.
AD1855
Burst Mode
To operate with SPI CCLK frequencies up to 12.288 MHz, the
SPI port can be operated in Burst Mode. This means that when
CLATCH is high, CCLK cannot be HI, as shown in Figure 8.
CLATCH
CCLK
>130ns
CDATA
20
40
60
80
100
120
140
160
180
TIME – ns
Figure 7. SPI Port Continuous CCLK Mode
CLATCH
CCLK
CDATA
200
400
600
800
1000
1200
TIME – ns
Figure 8. SPI Port Burst Mode
1400
1600
1800
REV. B
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