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SS8018

Command Byte Functions

The 8-bit command byte register (Table 5) is the master

index that points to the various other registers within the

SS8018. The register’s POR state is 0000 0000, so that

a Receive Byte transmission (a protocol that lacks the

command byte) that occurs immediately after POR re-

turns the current local temperature data.

The one-shot command immediately forces a new con-

version cycle to begin.

In software standby mode

after which the device returns to standby mode. If a

conversion is in progress when a one-shot command is

between conversions, a new conversion begins, the

conversion rate timer is reset, and the next automatic

conversion takes place after a full delay elapses.

Configuration Byte Functions

The configuration byte register (Table 6) is used to mask

interrupts and to put the device in software standby mode.

The other bits are empty.

Status Byte Functions

The status byte register (Table 7) indicates which (if any)

temperature thresholds have been exceeded. This byte

also indicates whether or not the ADC is converting and

whether there is an open circuit in the remote diode

DXP-DXN path. After POR, the normal state of all the

flag bits is zero, assuming none of the alarm conditions

are present. The status byte is cleared by any success-

ful read of the status, unless the fault persists. Note that

when the status flag bit is cleared.

When reading the status byte, you must check for inter-

nal bus collisions caused by asynchronous ADC timing,

or else disable the ADC prior to reading the status byte

one-shot mode, read the status byte only after the con-

version is complete, which is approximately 125ms max

after the one-shot conversion is commanded.

Table 5. Command-Byte Bit Assignments

REGISTER

COMMAND

POR STATE

FUNCTINON

RLTS

00h

0000 0000*

Read local temperature. It returns latest temperature

RRTE

01h

0000 0000*

Read remote temperature. It returns latest temperature

RSL

02h

N/A

Read status byte (flags, busy signal)

RCL

03h

0000 0000

Read configuration byte

RCRA

04h

0000 1000

Read conversion rate byte

RLHN

05h

0101 0101 (85)

RLLI

06h

0000 0000

RRHI

07h

0101 0101 (85)

RRLS

08h

0000 0000

WCA

09h

N/A

Write configuration byte

WCRW

0Ah

N/A

Write conversion rate byte

WLHO

0Bh

N/A

WLLM

0Ch

N/A

WRHA

0Dh

N/A

WRLN

0Eh

N/A

OSHT

0Fh

N/A

One-shot command (use send-byte format)

RTEXT

10h

0

Remote temperature extended byte

RTOFS

11h

0

Remote temperature offset high byte

RTOFSEXT

12h

0

Remote temperature offset extended byte

RLEXT

13h

0

RHEXT

14h

0

RTTHERM

19h

0101 0101 (85)

Remote temperature

THERM limit

LTTHERM

20h

0101 0101 (85)

Local temperature

THERM limit

THERMHYST

21h

0000 1010 (10)

THERM hysteresis

ALERTFQ

22h

0

ALERT

fault queue code

MFGIO

FEh

0100 0111

Manufacturer ID

DEVID

FFh

0000 0001

Device ID

*If the device is in standby mode at POR, both temperature registers read 0

°C.

Rev.2.01 6/06/2003