Datasheet
AD7870/AD7875/AD7876
Rev. C | Page 21 of 28
CONVST
12/8/CLK
2kΩ
+5V
–5V
4.7kΩ 4.7kΩ
CLKR
FSR
DR
SCLK
SSTRB
SDATA
ADSP-2101/
ADSP-2102
07730-029
TIMER
1
ADDITIONAL PINS OMITTED FOR CLARITY.
AD7870/
AD7875/
AD7876
1
TMS32020 Serial Interface
Figure 28 shows a serial interface between the AD7870/
AD7875/AD7876 and the TMS32020. The AD7870/AD7875/
AD7876 is configured for continuous clock operation. Note
that the ADC will not interface correctly to the TMS32020 if the
ADC is configured for a noncontinuous clock. Data is clocked
into the data receive register (DRR) of the TMS32020 during
conversion. As with the previous interfaces, when a 16-bit word
is received by the TMS32020 it generates an internal interrupt
to read the data from the DRR.
CONVST
12/8/CLK
2kΩ
5V
–5V
4.7kΩ 4.7kΩ
CLKR
FSR
DR
SCLK
SSTRB
SDATA
TMS32020
07730-028
TIMER
1
ADDITIONAL PINS OMITTED FOR CLARITY.
AD7870/
AD7875/
AD7876
1
Figure 29. ADSP-2101/ADSP-2102 Serial Interface
STANDALONE OPERATION
The AD7870/AD7875/AD7876 can be used in its Mode 2,
parallel interface mode for standalone operation. In this case,
conversion is initiated with a pulse to the ADC
CS
input. This
pulse must be longer than the conversion time of the ADC. The
BUSY
output is used to drive the
RD
input. Data is latched from
the ADC DB0–DB11 outputs to an external latch on the rising
edge of
BUSY
.
CS
t
CS
1
1
t
CS
>
t
16
+
t
CONVERT
.
2
ADDITIONAL PINS OMITTED FOR CLARITY.
BUSY
DB11
RD
DB0
EN
LATCH
07730-030
AD7870/
AD7875/
AD7876
2
Figure 28. TMS32020 Serial Interface
ADSP-2101/ADSP-2102 Serial Interface
Figure 29 shows a serial interface between the AD7870/
AD7875/AD7876 and the ADSP-2101/ADSP-2102. The ADC
is configured for continuous clock operation. Data is clocked
into the serial port register of the ADSP-2101/ADSP-2102
during conversion. As with the previous interfaces, when a 16-
bit data word is received by the ADSP-2101/ADSP-2102 an
internal microprocessor interrupt is generated and the data is
read from the serial port register.
Figure 30. Stand-Alone Operation