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SS8018

Table 6. Configuration-Byte Bit Assignments

BIT

NAME

POR STATE

FUNCTION

7 (MSB)

MASK

0

6

STOP

0

Standby mode control bit. If high, the device immediately stops converting and en-

ters standby mode. If low, the device converts in either one-shot or timer mode.

5-0

RFU

0

Reserved for future use

Table 7. Status-Byte Bit Assignments

BIT

NAME

FUNCTION

7 (MSB)

BUSY

A high indicates that the ADC is busy converting.

6

LHIGH*

A high indicates that the local high-temperature alarm has activated.

5

LLOW*

A high indicates that the local low-temperature alarm has activated.

4

RHIGH*

A high indicates that the remote high-temperature alarm has activated.

3

RLOW*

A high indicates that the remote low-temperature alarm has activated.

2

OPEN*

A high indicates a remote-diode continuity (open-circuit) fault.

1

RTHRM

0 (LSB)

LTHRM

*These flags stay high until cleared by POR, or until the status byte register is read.

Table 8. Conversion-Rate Control Byte

DATA

CONVERSION RATE (Hz)

00h

0.0625

01h

0.125

02h

0.25

03h

0.5

04h

1

05h

2

06h

4

07h

8

08h

16

09h to FFh

RFU

To check for internal bus collisions, read the status byte.

If the least significant seven bits are ones, discard the

data and read the status byte again. The status bits

LHIGH, LLOW, RHIGH, and RLOW are refreshed on the

SMBus clock edge immediately following the stop condi-

tion, so there is no danger of losing temperature-related

status data as a result of an internal bus collision. The

OPEN status bit (diode continuity fault) is only refreshed

at the beginning of a conversion, so OPEN data is lost.

byte register, so no false alerts are generated by an in-

ternal bus collision.

When auto-converting, if the THIGH and TLOW limits

are close together, it’s possible for both high-temp and

low-temp status bits to be set, depending on the amount

of time between status read operations (especially when

converting at the fastest rate). In these circumstances,

it’s best not to rely on the status bits to indicate reversals

in long-term temperature changes and instead use a

current temperature reading to establish the trend direc-

tion.

For bit 1 and bit 0, a high indicates a temperature alarm

happened for remote and local diode respectively. The

THERM

pin also asserts. These two bits wouldn’t be

cleared when reading status byte.

Conversion Rate Byte

The conversion rate register (Table 8) programs the time

interval

between

conversions

in

free-running

auto-convert mode. This variable rate control reduces

the supply current in portable-equipment applications.

The conversion rate byte’s POR state is 08h (16Hz).

The SS8018 looks only at the 4 LSB bits of this register,

so the upper 4 bits are “don’t care” bits, which should be

set to zero. The conversion rate tolerance is

±25% at

any rate setting.

Valid A/D conversion results for both channels are

available one total conversion time (125ms,typical) after

initiating a conversion, whether conversion is initiated

power-up.

Rev.2.01 6/06/2003