REV.

AD7665

–7–

PIN FUNCTION DESCRIPTION (continued)

Pin

No.

Mnemonic

Type

Description

21

D[8]

DO

When SER/

PAR is LOW, this output is used as Bit 8 of the Parallel Port Data Output Bus.

or SDOUT

When SER/

PAR is HIGH, this output, part of the Serial Port, is used as a serial data output

synchronized to SCLK. Conversion results are stored in an on-chip register. The AD7665

provides the conversion result, MSB first, from its internal shift register. The data format is

determined by the logic level of OB/

2C. In Serial Mode, when EXT/INT is LOW, SDOUT is

valid on both edges of SCLK.

In serial mode, when EXT/

INT is HIGH:

If INVSCLK is LOW, SDOUT is updated on the SCLK rising edge and valid on the next

falling edge.

If INVSCLK is HIGH, SDOUT is updated on the SCLK falling edge and valid on the next

rising edge.

22

D[9]

DI/O

When SER/

PAR is LOW, this output is used as Bit 9 of the Parallel Port Data Output Bus.

or SCLK

When SER/

PAR is HIGH, this pin, part of the Serial Port, is used as a serial data clock input

or output, dependent upon the logic state of the EXT/

INT pin. The active edge where the data

SDOUT is updated depends upon the logic state of the INVSCLK pin.

23

D[10]

DO

When SER/

PAR is LOW, this output is used as Bit 10 of the Parallel Port Data Output Bus.

or SYNC

When SER

/PAR is HIGH, this output, part of the Serial Port, is used as a digital output frame

synchronization for use with the internal data clock (EXT/

INT = Logic LOW). When a read

sequence is initiated and INVSYNC is LOW, SYNC is driven HIGH and remains HIGH

while SDOUT output is valid. When a read sequence is initiated and INVSYNC is HIGH,

SYNC is driven LOW and remains LOW while SDOUT output is valid.

24

D[11]

DO

When SER/

PAR is LOW, this output is used as Bit 11 of the Parallel Port Data Output Bus.

or RDERROR

When SER/

PAR is HIGH and EXT/INT is HIGH, this output, part of the Serial Port, is used as

an incomplete read error flag. In Slave Mode, when a data read is started and not complete when

the following conversion is complete, the current data is lost and RDERROR is pulsed HIGH.

25–28

D[12:15]

DO

Bit 12 to Bit 15 of the Parallel Port Data Output Bus. When SER/

PAR is HIGH, these outputs

are in high impedance.

29

BUSY

DO

Busy Output. Transitions HIGH when a conversion is started and remains HIGH until the

conversion is complete and the data is latched into the on-chip shift register. The falling edge

of BUSY could be used as a data-ready clock signal.

30

DGND

P

Must Be Tied to Digital Ground.

31

RD

DI

Read Data. When

CS and RD are both LOW, the Interface Parallel or Serial Output Bus is enabled.

32

CS

DI

Chip Select. When

CS and RD are both LOW, the Interface Parallel or Serial Output Bus is

enabled.

CS is also used to gate the external serial clock.

33

RESET

DI

Reset Input. When set to a logic HIGH, reset the AD7665. Current conversion, if any, is aborted.

If not used, this pin could be tied to DGND.

34

PD

DI

Power-Down Input. When set to a logic HIGH, power consumption is reduced and conversions

are inhibited after the current one is completed.

35

CNVST

DI

Start Conversion. A falling edge on

CNVST puts the internal sample-and-hold into the hold state

and initiates a conversion. In Impulse Mode (IMPULSE HIGH and WARP LOW), if

CNVST

is held LOW when the acquisition phase

(t

into the hold state and a conversion is immediately started.

36

AGND

P

Must Be Tied to Analog Ground.

37

REF

AI

Reference Input Voltage.

38

REFGND

AI

Reference Input Analog Ground.

39

INGND

AI

Analog Input Ground.

40, 41,

INA, INB,

AI

Analog Inputs. Refer to Table I for input range configuration.

42, 43

INC, IND

NOTES

AI = Analog Input

DI = Digital Input

DI/O = Bidirectional Digital

DO = Digital Output

P = Power

C