Interface Circuit
M0
M1
Decoder
MUX1
INTCLK
EXTCLK
RC
Oscillator
MUX3
Code
Generator
MUX4
MUX2
CLK/2
CLK/4
MDAT
MCLK
OCLK
CLK
DATA
∆∑
Modulator
AIN
FIGURE 5. Flexible Interface Block Diagram.
The code generator receives the clock signal from MUX1 and
generates the delta-sigma modulator clock (CLK) divided as
half clock (CLK/2) and quarter clock (CLK/4). At the same
time, the continuous data stream (DATA) coming from the
delta-sigma modulator is elaborated by the Code Generator.
Twinned binary coding (also known as split phase or Manches-
ter coding) is implemented and then output from the code
generator to MUX3.
The control signal from the decoder can select two different
modes on MCLK, one as an output of the internal clock signal
and another as the input for the external clock signal.
As a function of two control signals (M0 and M1), the decoder
circuit, using five control signals, will set multiplexers in order
to obtain the desired mode of operation.
DIFFERENT MODES OF OPERATION
MUX3 selects the source of the output bit stream data,
MDAT. The control signal coming from the decoder controls
the input source of MDAT. Two signals are coming in to the
MUX3, one directly from the delta-sigma modulator and the
other from the code generator. The control signal from the
decoder can select two different output modes on the signal
MDAT: bit stream from a delta-sigma modulator or twinned
binary coding of the same signal.
Figure 5 presents mode selectors (input signals M0 and M1)
that enter the flexible interface circuit and decoder that
decodes the input code, and select the desired mode of
operation. With two control lines it is possible to select four
different modes of operation mode 0, mode 1, mode 2, and
mode 3, which are shown in Table I.
MODE DEFINITION
M1
MO
The last control signal from the decoder controls MUX4.
MUX2 selects the input or output clock, the MCLK signal.
The control signal coming from the decoder controls the
direction of the clock. One signal entering MUX4 from MUX2
comes as a clock signal OCLK. Another signal leaves MUX4
and provides an input to MUX1 as an external clock, EXTCLK.
0
1
Internal Clock, Synchronous Data Output
LOW
LOW
LOW
HIGH
Internal Clock, Synchronous Data Output,
Half Output Clock Frequency
2
3
Internal Clock, Manchester Coded Data Output HIGH
External Clock, Synchronous Data Output
LOW
HIGH HIGH
TABLE I. Mode Definition and Description.
ADS1202
13
SBAS275
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BB [ BURR-BROWN CORPORATION ]
