AD7951 Analog Devices, AD7951 Datasheet - Page 30

• Manufacturer Part Number: AD7951
• Manufacturer: Analog Devices

Specifications of AD7951

• Resolution (bits): 14bit
• # Chan: 1
• Sample Rate: 1MSPS
• Interface: Byte,Par,Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni
• Ain Range: Bip 10V,Bip 5.0V,Uni 10V,Uni 5.0V
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

AD7951
MICROPROCESSOR INTERFACING
The AD7951 is ideally suited for traditional dc measurement
applications supporting a microprocessor, and ac signal
processing applications interfacing to a digital signal processor.
The AD7951 is designed to interface with a parallel 8-bit or
14-bit wide interface, or with a general-purpose serial port or
I/O ports on a microcontroller. A variety of external buffers can
be used with the AD7951 to prevent digital noise from coupling
into the ADC.
SPI Interface
The AD7951 is compatible with SPI and QSPI digital hosts and
DSPs such as Blackfin® ADSP-BF53x and ADSP-218x/ADSP-219x.
Figure 46 shows an interface diagram between the AD7951 and
the SPI-equipped ADSP-219x. To accommodate the slower
speed of the DSP, the AD7951 acts as a slave device, and data must
be read after conversion. This mode also allows the daisy-chain
feature. The convert command could be initiated in response to
an internal timer interrupt.
The reading process can be initiated in response to the end-of-
conversion signal (BUSY going low) using an interrupt line of
SCCLK
CNVST
SCCS
BUSY
SCIN
WARP = 0 OR 1
IMPULSE = 0 OR 1
X
t
t
33
31
t
31
START
1
BIP = 0 OR 1
TEN = 0 OR 1
t
34
BIPOLAR
2
HW/SW = 0
SER/PAR = 1
3
TEN
Figure 45. Serial Configuration Port Timing
4
t
PD
35
t
INVSCLK = 0
PD = 0
37
IMPULSE
t
5
36
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6
WARP
OB/2C
7
the DSP. The serial peripheral interface (SPI) on the ADSP-219x
is configured for master mode (MSTR) = 1, clock polarity bit
(CPOL) = 0, clock phase bit (CPHA) = 1, and SPI interrupt enable
(TIMOD) = 0 by writing to the SPI control register (SPICLTx).
It should be noted that to meet all timing requirements, the SPI
clock should be limited to 17 Mbps, allowing it to read an ADC
result in less than 1 μs. When a higher sampling rate is desired,
use one of the parallel interface modes.
8
DVDD
*ADDITIONAL PINS OMITTED FOR CLARITY.
Figure 46. Interfacing the AD7951 to SPI Interface
9
SER/PAR
EXT/INT
RD
INVSCLK
AD7951*
SDOUT
CNVST
BUSY
SCLK
t
8
CS
X
PFx
SPIxSEL (PFx)
MISOx
SCKx
PFx OR TFSx
ADSP-219x*