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DS1680

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PARALLEL INTERFACE

The ADC output is available on the data bus at pins D0–D7. A logic 0 on COEN will enable data onto the

data bus so that the DS1680 can be used in parallel with other devices. PEN_SELECT and

OUT_SELECT are used to decode which analog output (X-, Y-, AIN0, or AIN1) is output on the data bus

when COEN is asserted low. Since the device offers 10-bit resolution, the BHE pin is used to decode the

10 bits of data on the data bus. A logic 1 on BHE will enable data bits B2–B9. A logic 0 will enable data

bits B0–B1 along with the six LSBs = 0. The status pin (NEW_DATA ) pulses low to indicate that new

coordinate or conversion is available. The output can be read while NEW_DATA is low or after it has

gone high. Output selection and parallel data format is shown below.

OUTPUT SELECTION Table 4

PEN_SELECT OUT_SELECT ANALOG OUTPUT

0 0 AIN0

0 1 AIN1

1 0 X-

1 1 Y-

PARALLEL DATA FORMAT

MSB LSB

High Byte BHE = 1 B9 B8 B7 B6 B5 B4 B3 B2

Low Byte BHE = 0 B1 B0 0 0 0 0 0 0

POWER MANAGEMENT (ADC AND PEN-INPUT PROCESSOR)

The DS1680 analog circuitry can be placed into a low-power mode by asserting and holding the

PD_RESET pin at logic 1. Normal operation will resume when PD_RESET is returned to logic 0.

To further conserve power, the pen-detection circuitry will automatically switch the analog circuitry to

power-down mode whenever there is no pen input detected for more than three seconds. Normal

operation will automatically resume when any one of the following three events occur: pen down is

detected, the CONVERT signal is activated, or chip is reset (PD_RESET pulled to logic 1 and then

returned to logic 0).

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