begun, after which the device returns to standby mode.

If a conversion is in progress when a one-shot com-

mand is received, the command is ignored. If a one-

shot command is received in autoconvert mode

(RUN/STOP bit = 0) between conversions, a new con-

version begins, the conversion rate timer is reset, and

the next automatic conversion takes place after a full

delay elapses.

Fault Queue Function

To avoid false triggering of the MAX6695/MAX6696 in

noisy environments, a fault queue is provided, which

can be enabled by setting bit 5 (configuration register)

to 1. Four channel 1 fault or two channel 2 fault events

must occur consecutively before the fault output (OT2)

becomes active. Any reading that breaks the sequence

resets the fault queue counter. If there are three over-

limit readings followed by a within-limit reading, the

remote channel 1 fault queue counter is reset.

Configuration Byte Functions

The configuration byte register (Table 6) is a read-write

register with several functions. Bit 7 is used to mask

(disable) ALERT interrupts. Bit 6 puts the device into

software standby mode (STOP) or autonomous (RUN)

mode. Bit 5, when 1, enables the Fault Queue. Bit 4 is

reserved. Bit 3 is used to select either remote channel 1

or remote channel 2 for reading temperature data or for

setting or reading temperature limits. Bit 2 disables the

SMBus timeout, as well as the Alert Response. Bit 1

masks ALERT interrupt due to channel 2 when high. Bit

0 masks ALERT interrupt due to channel 1 when high.

Status Byte Functions

The status registers (Tables 7 and 8) indicate which (if

any) temperature thresholds have been exceeded and

if there is an open-circuit fault detected with the exter-

nal sense junctions. Status register 1 also indicates

whether the ADC is converting. After POR, the normal

state of the registers’ bits is zero (except bit 7 of status

register 1), assuming no alert or overtemperature con-

ditions are present. Bits 0 through 6 of status register 1

and bits 1 through 7 of status register 2 are cleared by

any successful read of the status registers, unless the

fault persists. The ALERT output follows the status flag

bit. Both are cleared when successfully read, but if the

condition still exists, they reassert at the end of the next

conversion.

The bits indicating OT1 and OT2 are cleared only on

reading status even if the fault conditions still exist.

Reading the status byte does not clear the OT1 and

OT2 outputs. One way to eliminate the fault condition is

for the measured temperature to drop below the tem-

perature threshold minus the hysteresis value. Another

way to eliminate the fault condition is by writing new

values for the RWO2E, RWO2I, RWO1E, RWO1I, or

HYST registers so that a fault condition is no longer

present.

close together, it is possible for both high-temp and

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

amount of time between Status Read operations. In

these circumstances, it is best not to rely on the status

bits to indicate reversals in long-term temperature

changes. Instead, use a current temperature reading to

establish the trend direction.

Dual Remote/Local Temperature Sensors with

SMBus Serial Interface

______________________________________________________________________________________

13

BIT

NAME

POR

STATE

FUNCTION

7(MSB)

MASK1

0

Mask ALERT interrupts when 1.

6

RUN/STOP

0

Standby mode control bit. If 1, immediately stops converting and enters

standby mode. If zero, it converts in either one-shot or timer mode.

5

Fault Queue

0

Fault queue enables when 1. When set to 1, four consecutive faults must occur

before OT2 output is asserted.

4

RFU

0

Reserved.

3

Remote 2 Select

0

0: Read/write remote 1 temperature and set-point values.

1: Read/write remote 2 temperature and set-point values.

2

SMB Timeout Disable

0

When set to 1, it disables the SMBus timeout, as well as the alert response.

1

MASK Alert Channel 2

0

When set to 1, it masks ALERT interrupt due to channel 2.

0

MASK Alert Channel 1

0

When set to 1, it masks ALERT interrupt due to channel 1.

Table 6. Configuration Byte Functions