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SS8017

Rev.2.01 6/06/2003

Table 4. Command-Byte Bit Assignments

COMMAND

POR STATE

FUNCTION

RRTE2

00h

0000 0000b

Read 2nd remote temperature: returns latest temperature

RRTE1

01h

0000 0000b

Read 1st remote temperature: returns latest temperature

RSL

02h

N/A

Read status byte (flags, busy signal)

RCL

03h

0000 0000b

Read configuration byte

RCRA

04h

0000 0010b

Read conversion rate byte

RRHI2

05h

0111 1111b (127) Read 2nd remote THIGH limit

RRLS2

06h

1100 1001b(-55)

Read 2nd remote TLOW limit

RRHI1

07h

0111 1111b (127) Read 1st remote THIGH limit

RRLS1

08h

1100 1001b (-55) Read 1st remote TLOW limit

WCA

09h

N/A

Write configuration byte

WCRW

0Ah

N/A

Write conversion rate byte

WRHA2

0Bh

N/A

Write 2nd remote THIGH limit

WRLN2

0Ch

N/A

Write 2nd remote TLOW limit

WRHA1

0Dh

N/A

Write 1st remote THIGH limit

WRLN1

0Eh

N/A

Write 1st remote TLOW limit

OSHT

0Fh

N/A

One-shot command (use send-byte format)

TCRIT1

35h

0110 1100b (108) Critical temperature for 1

st remote temperaure sensor

TCRIT2

36h

0101 1000b (88)

Critical temperature for 2

nd remote temperaure sensor

The Alert Response can activate several different slave

devices simultaneously, similar to the SMBus General

Call. If more than one slave attempts to respond, bus

arbitration rules apply, and the device with the lower

address code wins. The losing device does

not generate an acknowledge and continues to hold

the

ALERT line low until serviced (implies that the

host interrupt input is level sensitive). Successful

reading of the alert response address clears the inter-

rupt latch.

Command Byte Functions

The 8-bit command byte register (Table 4) is the mas-

ter index that points to the various other registers

within the SS8017. 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 returns the current local temperature data.

The one-shot command immediately forces a new con-

version cycle to begin. In software standby mode

( RUN /STOP bit = high), a new conversion is begun,

after which the device returns to standby mode. If a

conversion is in progress when a one-shot command is

received in auto-convert mode (RUN/STOP bit = low)

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 contents are listed in

table 5. Bit 7 (MASK) is used to mask

ALERT inter-

rupt. Bit 6 (RUN /STOP) is to put the device in software

standby mode. Setting bit 5 (DET_FAN) with logic 1

can activate the detection of fan failure. Logic 1 in bit 4

(EN_TH_SHUT) makes thermal shutdown function valid

and logic 0 disables this function and keep TH_SHUT

pin low. Bit 3~0 forms thermal shutdown fault queue.

The number of faults these bits decided are listed in

table 6.

Thermal Status Byte Functions

The thermal status byte register (02h) (Table 6) indi-

cates 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 DXPx-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 successful read of the status, unless

the fault persists. Note that the ALERT interrupt latch

is not automatically cleared when the status flag bit is

cleared.

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

ternal bus collisions caused by asynchronous ADC

timing, or else disable the ADC prior to reading the

status byte (via the RUN /STOP bit in the configuration

byte). In one-shot mode, read the status byte only after

the conversion is complete, which is 150ms max after

the one-shot conversion is commanded.

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