1°C Triple SMBus Sensor with Resistance Error Correction
Datasheet
Chapter 3 System Management Bus Interface Protocol
A host controller, such as an SMSC I/O controller, communicates with the EMC1033 via the two wire
serial interface named SMBus. The SMBus interface is used to read and write registers in the
EMC1033, which is a slave-only device. A detailed timing diagram is shown in Figure 3.1.
TLOW
THIGH
THD:STA
TSU:STO
TR
TF
SMCLK
THD:STA
THD:DAT TSU:DAT
TSU:STA
SMDATA
TBUF
S
S
P
P
S - Start Condition
P - Stop Condition
Figure 3.1 System Management Bus Timing Diagram
The EMC1033 implements a subset of the SMBus specification and supports Write Byte, Read Byte,
Send Byte, Receive Byte, and Alert Response Address protocols. as shown. In the tables that describe
the protocol, the “gray” columns indicate that the slave is driving the bus.
3.1
Write Byte
The Write Byte protocol is used to write one byte of data to the registers as shown below:
Table 3.1 SMBus Write Byte Protocol
START
SLAVE ADDRESS
WR
ACK
COMMAND
ACK
DATA
ACK
STOP
1
7
1
1
8
1
8
1
1
3.2
Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown below:
Table 3.2 SMBus Read Byte Protocol
START SLAVE ADDRESS
WR
ACK
COMMAND
ACK
START
SLAVE ADDRESS
RD
ACK
DATA
NACK
STOP
1
7
1
1
8
1
1
7
1
1
8
1
1
3.3
Send Byte
The Send Byte protocol is used to set the Internal Address Register to the correct Address. The Send
Byte can be followed by the Receive Byte protocol described below in order to read data from the
register. The send byte protocol cannot be used to write data - if data is to be written to a register then
the write byte protocol must be used as described in subsection above. The send byte protocol is
shown in Table 3.3, “SMBus Send Byte Protocol,” on page 7.
Table 3.3 SMBus Send Byte Protocol
FIELD:
START
SLAVE ADDR
WR
ACK
REG. ADDR
ACK
STOP
Bits:
1
7
1
1
8
1
1
SMSC EMC1033
7
Revision 1.1 (01-19-07)
DATASHEET
SMSC [ SMSC CORPORATION ]
