AD7994/AD7993

–16–

REV. PrF

PRELIMINARYTECHNICAL DATA

Bit

Mnemonic

Comment

D7-D4 CH4-CH1

These four channel address bits select the analog input channel(s) to be converted on.

A 1 in any of bits D7 to D4 selects a channel for conversion. If more than one channel bit is

set to 1 then the AD7994/AD7993 will sequence through the selected channels, starting with

the lowest channel. All unused channels should be set to zero. Table V shows how these four

channel address bits are decoded. Prior to initiating a conversion a channel(s) must be

selected in the Configuration Register.

D 3

F L T R

The value written to this bit of the Control Register determines whether the filtering on SDA

and SCL is enabled or to be bypassed. If this bit is a 1 then the the filtering is enabled, if it is

a 0, then the filtering is bypassed.

D 2

ALERT EN

The hardware ALERT function is enabled if this bit is set to 1 and disabled if set to 0. This bit

is used in conjunction with the BUSY/ALERT bit to determine if the ALERT/BUSY pin will

act as an ALERT or a BUSY output. (See Table VI.)

D 1

BUSY/ALERT

This bit is used in conjunction with the ALERT EN bit to determine if

the ALERT/BUSY

output, pin 13, will act as an ALERT or BUSY output (see TABLE V1), or if pin 13 is

configured as an ALERT output pin, if it is to be reset. When reading the Configuration

registerD1 will always be a 0 when D2 is a 1.

D 0

BUSY/ALERT

This bit determines the active polarity of the ALERT/BUSY pin regardless of whether it is

POLARITY

configured as an ALERT or BUSY output. It is active low if this bit is set to 0, and it is active

high if set to 1.

CONFIGURATION REGISTER

The Configuration Register is an 8-bit read/write register that is used to set the operating modes of the AD7994/

AD7993. The bit functions of all 8 bits of the Configuration Register are outlined in Table IV.

Table IV.

Configuration Register Bit Function Description

D7

D6

D5

D4

D3

D2

D1

D0

CH4

CH3

CH2 CH1

F L T R ALERT EN

BUSY/ALERT

ALERT/BUSY POLARITY

0*

0*

0*

0*

1*

0*

0*

0*

*Default settings at Power-up