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DS1800 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

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DS1800
Dallas
Dallas Semiconductor -> Maxim Integrated Dallas
DS1800 Datasheet PDF : 14 Pages
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DS1800
3-WIRE SERIAL INTERFACE CONTROL
CPU control of the DS1800 is accomplished using the 3-wire serial port of the device. This interface
drives an internal control logic unit. Direct wiper positioning is accomplished by using this port which
consist of three input signals: RST , CLK, and D.
The RST control signal is used to enable 3-wire serial port write operations. The CLK terminal is an input
that provides synchronization for data I/O. Data is input bit by bit via the D input signal pin.
The 3-wire serial timing diagrams are provided in Figure 5. Serial port operation or activity begins with
the transition of the RST signal from a low state to a high state. Once activated, data is clocked into the
part on the low to high transition of the CLK signal input. Data input via the D terminal is transferred in
order of the desired potentiometer-0 wiper value, followed by the potentiometer-1 wiper position value.
Two 8-bit values are used to store wiper position for each potentiometer during powered conditions.
These 8-bit values are written to a 16-bit I/O shift register. A detailed diagram of the 16-bit I/O shift
register is shown in Figure 6.
Bits 0 through 7 are reserved for the positioning of wiper-0 while bits 8 through 15 are reserved for
control of wiper-1. Bits 0 through 6 are used for actual wiper positioning of potentiometer-0. Bit 7 is used
to mute potentiometer-0. If this bit is set to a 1, the potentiometer-0 wiper will be connected to the OUT0
end of the resistor array regardless of the settings of bits 0 through 6.
Bits 8 through 15 are used for positioning the wiper of potentiometer-1. Bits 8 through 14 control wiper
position on the resistor array. Bit 15 is used for muting potentiometer-1. Bit 15, like bit 7, when set to 1
will mute potentiometer 1, regardless of the settings of bits 8 through 14.
Data is transmitted LSB first starting with bit 0. A complete transmission of 16 bits of data is required to
insure proper setting of each potentiometer’s wiper. An incomplete transmission may result in undesired
wiper settings.
Once the 16 bits of information has been transmitted and the RST signal input transitions to a low state,
the new wiper positions are loaded into the part.
PUSHBUTTON INTERFACE CONTROL
The DS1800 can be configured to operate from contact closure or pushbutton inputs. The pushbutton
inputs consist of signals P0A, P0G, P1A, P1G and MUTE. P0A and P0G allow attenuation and gain
control of the input signal to potentiometer-0, while P1A and P1G provide the same control for
potentiometer-1. The MUTE input provides a toggle control for muting the potentiometers via
pushbutton.
The P0A and P1A control inputs, based on the recommended circuit configuration, are used to attenuate
the incoming signal by moving the wiper position towards the OUTx terminals. The P0G and P1G control
inputs provide the opposite function; positioning the wiper(s) closer to the INx terminals, thus providing
gain.
Each of these control inputs is internally pulled up via a 50 kΩ=resistance. Additionally, these inputs
require no external components for debouncing or timing which are provided internal to the part.
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