Rainbow-electronics MAX6622 Manual do Utilizador descarregar pdf (Página 8)

MAX6622

conversion results until they have been read. If the most

significant bits have not been read within an SMBus

timeout period (nominally 37ms), normal updating con-

tinues. Table 1 shows the main temperature register

(high byte) data format, and Table 2 shows the extend-

ed resolution register (low byte) data format.

Diode Fault Detection

If a channel’s input DXP_ and DXN_ are left open, the

MAX6622 detects a diode fault. An open diode fault

does not cause either ALERT or OVERT to assert. A bit in

the status register for the corresponding channel is set to

1 and the temperature data for the channel is stored as

all 1s (FFh). It takes approximately 4ms for the MAX6622

to detect a diode fault. Once a diode fault is detected,

the MAX6622 goes to the next channel in the conversion

sequence. Depending on operating conditions, a short-

ed diode may or may not cause ALERT or OVERT to

assert, so if a channel will not be used, its DXN and DXP

inputs should be left unconnected.

5-Channel Precision Temperature Monitor

8 _______________________________________________________________________________________

Write Byte Format

Read Byte Format

Send Byte Format

Receive Byte Format

SLAVE ADDRESS: EQUIVALENT

TO CHIP-SELECT LINE OF A

3-WIRE INTERFACE

COMMAND BYTE: SELECTS TO

WHICH REGISTER YOU ARE

WRITING

DATA BYTE: DATA GOES INTO THE REGISTER

SET BY THE COMMAND BYTE (TO SET

THRESHOLDS, CONFIGURATION MASKS, AND

SAMPLING RATE)

SLAVE ADDRESS: EQUIVALENT

TO CHIP-SELECT LINE

COMMAND BYTE: SELECTS

FROM WHICH REGISTER YOU

ARE READING

SLAVE ADDRESS: REPEATED

DUE TO CHANGE IN DATA-

FLOW DIRECTION

DATA BYTE: READS FROM

THE REGISTER SET BY THE

COMMAND BYTE

COMMAND BYTE: SENDS COM-

MAND WITH NO DATA, USUALLY

USED FOR ONE-SHOT COMMAND

DATA BYTE: READS DATA FROM

THE REGISTER COMMANDED BY

THE LAST READ BYTE OR WRITE

BYTE TRANSMISSION; ALSO

USED FOR SMBus ALERT

RESPONSE RETURN ADDRESS

S = START CONDITION. SHADED = SLAVE TRANSMISSION.

P = STOP CONDITION. /// = NOT ACKNOWLEDGED.

S ADDRESS RD ACK DATA /// P

7 bits 8 bits

WRS ACK COMMAND ACK P

8 bits

ADDRESS

7 bits

ACKDATA

8 bits

ACKCOMMAND

8 bits

ACKWRADDRESS

7 bits

S ADDRESS WR ACK COMMAND ACK S ADDRESS

7 bits8 bits7 bits

RD ACK DATA

8 bits

/// P

Figure 2. SMBus Protocols

TEMP (°C) DIGITAL OUTPUT

> +127 0111 1111

+127 0111 1111

+126 0111 1110

+25 0001 1001

0 0000 0000

< 0 0000 0000

Diode fault (open) 1111 1111

Diode fault (short) 1111 1111 or 1110 1110

Table 1. Main Temperature Register

(High-Byte) Data Format

TEMP (°C) DIGITAL OUTPUT

0 000X XXXX

+0.125 001X XXXX

+0.250 010X XXXX

+0.375 011X XXXX

+0.500 100X XXXX

+0.625 101X XXXX

+0.725 110X XXXX

+0.875 111X XXXX

Table 2. Extended Resolution Temperature

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 17 18

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