XRD9825 Datasheet, PDF (27/33 Pages) Exar Corporation – 16-Bit Linear CIS/CCD Sensor Signal Processor with Serial Control

XRD9825
Serial Load Control Registers
The serial load registers are controlled by a three wire
serial interface through the bi-directional parallel port to
reduce the pin count of this device. When SYNCH is set
to high, the output bus is tri-stated and the serial
interface is activated. DB7/LD, DB5/SCLK and DB6/
SDATA are the three input signals that control this
process. The DB7/LD signal is set low to initiate the
loading of the internal registers.
There are internal registers that are accessed via an 11-
bit data string. Data is shifted in on the rising edge of
SCLK and loaded to the registers on the rising edge of
LD. The data on pin DB6/SDATA is latched automati-
cally after eleven DB5/SCLKs have been counted. If
eleven clocks are not present on DB5/SCLK before the
DB7/LD signal returns high, no data will be loaded into
the internal registers. If more than 11 clocks are
present on DB5/SCLK, the additional clocks will be
ignored. The data corresponding to the first eleven
DB5/SCLKs will be loaded only.
The first three MSBs choose which internal register will
be selected. The remaining 8 LSBs contain the data
needed for programming the internal register for a
particular configuration.
Power-Up State of the Internal Registers
The control register settings upon initial power-up are
for CIS, DC Coupled configuration (VRT is set to
internal, Input DC Reference=AGND and the input to
the ADC is selected through the RED channel). Gain is
unity and Offset is set to zero. The test modes are
disabled in the power-up state.
SYNCH
DB7/LD
DB5/SCLK
DB6/SDATA
tsclkw
tdz
tds tdh
S2 S1 S0 D7
Figure 21. Write Timing
tdl
D2 D1 D0
Rev. 1.00
27