Rainbow Electronics MAX6622 - Manual (Page 7)

SMBus Digital Interface
From a software perspective, the MAX6622 appears as
a series of 8-bit registers that contain temperature mea-
surement data, alarm threshold values, and control bits.
A standard SMBus-compatible, 2-wire serial interface is
used to read temperature data and write control bits
and alarm threshold data. The same SMBus slave
address also provides access to all functions.
The MAX6622 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 2). The shorter receive byte protocol allows
quicker transfers, provided that the correct data regis-
ter was previously selected by a read byte instruction.
Use caution with the shorter protocols in multimaster
systems, since a second master could overwrite the
command byte without informing the first master. Figure
3 is the SMBus write timing diagram and Figure 4 is the
SMBus read timing diagram.
The remote diode 1 measurement channel provides 11
bits of data (1 LSB = +0.125°C). All other temperature-
measurement channels provide 8 bits of temperature
data (1 LSB = +1°C). The 8 most significant bits (MSBs)
can be read from the local temperature and remote
temperature registers. The remaining 3 bits for remote
diode 1 can be read from the extended temperature
register. If extended resolution is desired, the extended
resolution register should be read first. This prevents
the most significant bits from being overwritten by new
MAX6622
5-Channel Precision Temperature Monitor
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Figure 1. Internal Block Diagram
DXP1
DXN1
DXP2
DXN2
DXP3
DXN3
DXP4
DXN4
INPUT
BUFFER
10/100 μA
V CC
REF
COUNT
COUNTER
COMMAND BYTE
REMOTE TEMPERATURES
LOCAL TEMPERATURES
REGISTER BANK
ALERT THRESHOLD
OVERT THRESHOLD
ALERT RESPONSE ADDRESS
ALARM
ALU
ADC
SMBus
INTERFACE
MAX6622
SMBCLK SMBDATA
OVERT
AVERT
STBY