ht82v42 Holtek Semiconductor Inc., ht82v42 Datasheet - Page 13

• Manufacturer Part Number: ht82v42
• Description: Cis Analog Signal Processor
• Manufacturer: Holtek Semiconductor Inc.

References
The ADC reference voltages are derived from an inter-
nal bandgap reference, and buffered to pins VRT and
VRB, where they must be decoupled to ground. Pin
VRX is driven by a similar buffer, and also requires de-
coupling. The output buffer from the RLCDAC also re-
quires decoupling at pin VRLC/VBIAS.
Power Supply
The HT82V42 can run from a single 3.3V single supply.
Power Management
Power management for the device is performed via the
Control Interface. The device can be powered on or off
completely by clearing the EN bit low.
All the internal registers maintain their previously pro-
grammed value in the power down mode while the Se-
rial Interface inputs remain active.
Rev. 1.00
Internal VSMP Pulse Generated by Programmable Internal Sample Detect Circuit
13
Line-by-Line Operation
Certain linear sensors (e.g. Contact Image Sensors)
give a colour output on a line-by-line basis. i.e. a full line
of red pixels followed by a line of green pixels followed
by a line of blue pixels.
In this mode the input multiplexer and (optionally) the
PGA/Offset register multiplexers can be auto-cycled by
the application of pulses to the RLC/ACYC input pin by
setting the ACYCNRLC register bit. See Figure for de-
tailed timing information. The multiplexers change on
the first DCLK rising edge after RLC/ACYC is taken
high. A write to the auto-cycle reset register causes
these multiplexers to be reset, selecting the colour R
and the RED offset/gain registers. Alternatively, all three
multiplexers can be controlled via the serial interface by
writing to register bits INTM[1:0] to select the desired
colour. It is also possible for the input multiplexer to be
controlled separately from the PGA and Offset
multiplexers. Table describes all the multiplexer selec-
tion modes that are possible.
November 20, 2009
HT82V42