Datasheet

AD7622
Rev. 0 | Page 26 of 28
MICROPROCESSOR INTERFACING
The AD7622 is ideally suited for traditional dc measurement
applications supporting a microprocessor, and ac signal processing
applications interfacing to a digital signal processor. The
AD7622 is designed to interface with a parallel 8-bit or 16-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 AD7622 to prevent digital noise from coupling into the
ADC. The
SPI Interface (ADSP-219x) section illustrates the use
of the AD7622 with the ADSP-219x SPI-equipped DSP.
SPI Interface (ADSP-219x)
Figure 42 shows an interface diagram between the AD7622 and
an SPI-equipped DSP, the ADSP-219x. To accommodate the
slower speed of the DSP, the AD7622 acts as a slave device and
data must be read after conversion. This mode also allows the
daisy-chain feature. The convert command can be initiated in
response to an internal timer interrupt. The 16-bit output data
are read with three SPI byte access. 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 the SPI interrupt enable (TIMOD) = 00 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, it is
recommended to use one of the parallel interface modes.
BUSY
CS
SDOUT
SCLK
CNVST
AD7622
PFx
SPIxSEL (PFx)
MISOx
SCKx
PFx OR TFSx
ADSP-219x
1
DVDD
MODE0
MODE1
EXT/INT
RD
INVSCLK
1
ADDITIONAL PINS OMITTED FOR CLARITY.
06023-040
Figure 42. Interfacing the AD7622 to ADSP-219x