Rainbow Electronics MAX6642 - Manual (Page 6)

MAX6642
register was previously selected by a Write Byte
instruction. Use caution when using the shorter proto-
cols in multimaster systems, as a second master could
overwrite the command byte without informing the first
master.
Read temperature data from the read internal tempera-
ture (00h) and read external temperature (01h) regis-
ters. The temperature data format for these registers is
8 bits for each channel, with the LSB representing +1°C
(Table 1).
Read the additional bits from the read extended tem-
perature byte register (10h, 11h), which extends the
data to 10 bits and the resolution to +0.25
°C per LSB
(Table 2).
±1°C, SMBus-Compatible Remote/Local
Temperature Sensor with Overtemperature Alarm
6 _______________________________________________________________________________________
S ADDRESS WR ACK ACK P DATA ACK COMMAND
7 BITS 1 8 BITS 8 BITS
SLAVE ADDRESS: EQUIVA-
LENT TO CHIP-SELECT LINE OF
A 3-WIRE INTERFACE DATA BYTE: DATA GOES INTO THE REGISTER
SET BY THE COMMAND BYTE (TO SET
THRESHOLDS, CONFIGURATION MASKS, AND
SAMPLING RATE)
WRITE BYTE FORMAT
S ADDRESS ADDRESS WR ACK ACK P S RD ACK /// DATA COMMAND
7 BITS 7 BITS 8 BITS 8 BITS
READ BYTE FORMAT
SLAVE ADDRESS: EQUIVA-
LENT TO CHIP SELECT LINE COMMAND BYTE: SELECTS
WHICH REGISTER YOU ARE
REDING FROM
S P ADDRESS WR ACK ACK COMMAND
7 BITS 8 BITS
SEND BYTE FORMAT
COMMAND BYTE: SENDS COM-
MAND WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
S P ADDRESS RD ACK /// DATA
7 BITS 8 BITS
RECEIVE BYTE FORMAT
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
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
S = START CONDITION
P = STOP CONDITION SHADED = SLAVE TRANSMISSION
/// = NOT ACKNOWLEDGED
Figure 1. SMBus Protocols
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
A B C D E F G H I J
SMBDATA
t SU:STA t HD:STA
t LOW t HIGH
t SU:DAT
t SU:STO t BUF
L M K
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 2. SMBus Write Timing Diagram