AD7870SQ Analog Devices Inc, AD7870SQ Datasheet - Page 19

• Manufacturer Part Number: AD7870SQ
• Description: IC ADC 12BIT SAMPLING 3V 24-CDIP
• Manufacturer: Analog Devices Inc

Specifications of AD7870SQ

• Rohs Status: RoHS non-compliant
• Number Of Bits: 12
• Sampling Rate (per Second): 100k
• Data Interface: Serial, Parallel
• Number Of Converters: 1
• Power Dissipation (max): 95mW
• Voltage Supply Source: Dual ±
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: 24-CDIP (0.300", 7.62mm)

MICROPROCESSOR INTERFACE
The AD7870/AD7875/AD7876 have a wide variety of
interfacing options. They offer two operating modes and
three data-output formats. Fast data access times allow
direct interfacing to most microprocessors including the
DSP processors.
PARALLEL READ INTERFACING
Figure 22, Figure 23, and Figure 24 show interfaces to the
ADSP-2100, TMS32010 and the TMS32020 DSP processors.
The ADC is operating in Mode 1, parallel read for all three
interfaces. An external timer controls conversion start asyn-
chronously to the microprocessor. At the end of each conversion
the ADC BUSY / INT interrupts the microprocessor. The
conversion result is read from the ADC with the following
instruction:
ADSP-2100: MR0 = DM(ADC)
TMS32010: IN D,ADC
TMS32020: IN D,ADC
MR0 = ADSP-2100 MR0 Register
D = Data Memory Address
ADC = AD7870/AD7875/AD7876 Address
Some applications may require that conversions be initiated by
the microprocessor rather than an external timer. One option
is to decode the CONVST signal from the address bus so that a
write operation to the ADC starts a conversion. Data is read at
the end of conversion as described earlier. Note: a read
operation must not be attempted during conversion.
1
ADDITIONAL PINS OMITTED FOR CLARITY.
ADSP-2100
DMA13
DMD15
DMRD
DMA0
DMD0
Figure 22. ADSP-2100 Parallel Interface
IRQn
DMS
ADDRESS BUS
EN
DECODE
ADDR
DATA BUS
TIMER
5V
CONVST
CS
12/8/CLK
BUSY/INT
RD
DB11
DB0
AD7870/
AD7875/
AD7876
1
Rev. C | Page 19 of 28
TWO-BYTE READ INTERFACING
68008 Interface
Figure 25 shows an 8-bit bus interface for the MC68008 micro-
processor. For this interface, the 12/ 8 /CLK input is tied to 0 V
and the DB11/HBEN pin is driven from the microprocessor
least significant address bit. Conversion start control is provided
by the microprocessor. In this interface example, a Move instruc-
tion from the ADC address both starts a conversion and reads
the conversion result.
MOVEW ADC,DO
ADC = AD7870/AD7875/AD7876 address
D0 = 68008 D0 register
1
1
ADDITIONAL PINS OMITTED FOR CLARITY.
ADDITIONAL PINS OMITTED FOR CLARITY.
TMS32010
TMS32020
STRB
Figure 23. TMS32010 Parallel Interface
Figure 24. TMS32020 Parallel Interface
MEN
INTn
DEN
R/W
PA2
PA0
D15
A15
D15
INT
D0
A0
D0
IS
ADDRESS BUS
ADDRESS BUS
AD7870/AD7875/AD7876
EN
EN
DECODE
DECODE
ADDR
ADDR
DATA BUS
DATA BUS
TIMER
TIMER
5V
5V
CONVST
CS
12/8/CLK
BUSY/INT
RD
DB11
DB0
CONVST
CS
12/8/CLK
BUSY/INT
RD
DB11
DB0
AD7870/
AD7875/
AD7876
AD7870/
AD7875/
AD7876
1
1