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Revision 1.02

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AS1530/AS1531

Control Register

The control register on the AS1530/AS1531 is a 8-bit, write-only register. Data is written to this register using the CSN,

DIN and SCLK pins. The control register format is shown in Table 7 and the function of the bits are defined in Table 8.

The AS1530/AS1531 operating modes are selected by sending an 8-bit data word to the internal shift register via pin

DIN. After pin CSN is pulled low, the first logic 1 on pin DIN is interpreted as a start bit. A start bit is defined as one of

the following:

!

!

The first logic 1 bit clocked into pin DIN after bit 6 of a conversion in progress is clocked out of pin DOUT.

Figure 22 on page 17 shows the serial-interface timing necessary to perform a conversion every 16 SCLK cycles. If

CSN is tied low and SCLK is continuous, guarantee a start bit by first clocking in sixteen 0s. The fastest speed at which

the devices can operate is 16 clocks per conversion (with CSN held low between conversions).

Analog Input Configuration

Table 7. Control Byte Format

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

START (MSB)

SEL2

SEL1

SEL0

RANGE

MODE

PD1

PD0 (LSB)

Table 8. Bit Descriptions

Bit

Name

Description

7

START

The first logic 1 bit after CSN goes low signifies the start of a control byte.

6:4

SEL2:SEL0

These three bits select which of the eight channels and pin COM are used for

the conversion (see Table 10 and Table 11).

3

RANGE

This bit selects the analog input range of the AS1530/AS1531.

2

MODE

This bit in conjunction with bit RANGE changes the analog input configuration.

0 = The voltage difference between two selectable channels is converted. This

setting selects two's complement coding (see Table 10 on page 16 and

Table 11 on page 16).

1 = One of the eight input channels is referenced to COM. This setting also

selects binary coding.

1:0

PD1:PD0

Selects the AS1530/AS1531 operating mode:

PD1

PD0

Mode

0

0

Full power-down mode.

0

1

Reduced-power mode.

1

0

Reduced-power mode.

1

1

Normal operation.

Table 9. Analog Input Configuration

Analog Input Configuration

Mode

Range

Coding

Comments

8-Channel Single-Ended

1

1

Binary

COM should be tied to GND.

8-Channel Pseudo Differential

referenced to COM

1

1

Binary

8-Channel Pseudo Differential

referenced to COM

1

0

Binary

4-Channel Pseudo Differential

0

1

Two's Complement

4-Channel Pseudo Differential

0

0

Two's Complement

4-Channel Fully Differential

0

0

Two's Complement

fully differential input signal.