AD7951
Data Sheet
Rev. A | Page 30 of 32
SCIN
SCCLK
WARP
TEN
123
67
BUSY
HW/SW = 0
INVSCLK = 0
CNVST
SCCS
t8
t36
t35
t37
4
PD
5
BIPOLAR
IMPULSE
OB/2C
X
89
SER/PAR = 1
BIP = 0 OR 1
TEN = 0 OR 1
IMPULSE = 0 OR 1
WARP = 0 OR 1
PD = 0
t33
t34
t31
X
t31
06
39
6-
0
45
START
Figure 45. Serial Configuration Port Timing
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
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.
BUSY
CS
SDOUT
SCLK
CNVST
AD7951*
PFx
SPIxSEL (PFx)
MISOx
SCKx
PFx OR TFSx
ADSP-219x*
*ADDITIONAL PINS OMITTED FOR CLARITY.
DVDD
SER/PAR
EXT/INT
RD
INVSCLK
06
39
6-
0
46
Figure 46. Interfacing the AD7951 to SPI Interface