Rainbow Electronics MAX6656 - Manual (Page 7)

SMBus Digital Interface
From a software perspective, the MAX6655/MAX6656
appear as a set of byte-wide registers that contain tem-
perature data, voltage data, alarm threshold values,
and control bits. Use a standard SMBus 2-wire serial
interface to read temperature data and write control
bits and alarm threshold data.
The MAX6655/MAX6656 employ four standard SMBus
protocols: Write Byte, Read Byte, Send Byte, and
Receive Byte (Figures 1, 2, and 3). The two shorter pro-
tocols (Receive and Send) allow quicker transfers, pro-
vided that the correct data register was previously
selected by a Write or Read Byte instruction. Use cau-
tion with the shorter protocols in multimaster systems,
since a second master could overwrite the Command
Byte without informing the first master.
MAX6655/MAX6656
Dual Remote/Local Temperature Sensors and
Four-Channel Voltage Monitors
_______________________________________________________________________________________ 7
SMBCLK
A B C D E F G H I J K
SMBDATA
t SU:STA
t HD:STA
t
LOW
t
HIGH
t SU:DAT t HD:DAT t SU:STO t BUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
L M
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/I 2 C Write Timing Diagram
SMBCLK
A B C D E F G H I J K
SMBDATA
t SU:STA t HD:STA
t LOW t HIGH
t SU:DAT t HD:DAT t SU:STO t BUF
L M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
Figure 3. SMBus/I 2 C Read Timing Diagram