Environmental Monitoring and Control Device
Datasheet
Table 5.2 - SMBus Read Byte Protocol
SLAVE
ADDR
REG.
SLAVE
ADDR
REG.
FIELD: START
BITS:
WR
ACK
ACK START
RD ACK
NACK STOP
ADDR
DATA
1
7
1
1
8
1
1
7
1
1
8
1
1
Send Byte
The Send Byte protocol is used to set the Internal Address Register to the correct register in the EMC
Register Block. No data is transferred for a Send Byte protocol. 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 the table below.
Table 5.3 - SMBus Send Byte Protocol
SLAVE
ADDR
REG.
FIELD: START
BITS:
WR ACK
ACK STOP
ADDR
1
7
1
1
8
1
1
Receive Byte
The Receive Byte protocol is used to read data from the registers when the register address is known to
be at the desired address (using the Internal Address Register). This is used when the register address
has been written to the desired address using the Send Byte protocol. This can be used for successive
reads of the same register. The data will only be read if the protocol shown in Table 5.4 is performed
correctly. Only one byte is transferred at time for a Receive Byte protocol.
Table 5.4 - SMBus Receive Byte Protocol
SLAVE
FIELD: START
BITS:
RD ACK REG. DATA
NACK
STOP
ADDR
1
7
1
1
8
1
1
5.4
Invalid Protocol Response Behavior
Registers that are accessed with an invalid protocol will not be updated. A register will only be updated
following a valid protocol. The only valid protocols are the Write Byte, Read Byte, Send Byte, and Receive
Byte protocols, which are described above.
The EMC6D100/EMC6D101 device responds to three SMBus slave addresses:
1) The SMBus slave address that supports the valid protocols defined in the previous sections
is determined by the level on the Address Select and Address Enable pins as shown in
section 5.1 Slave Address on page 16.
2) SMBus General Call Address (0001 100). The SMBus will only respond to the General Call
Address if the SMBus Alert Response interrupt was generated to request a response from
the Host. The SMBus Allert Response is defined in section 5.10 SMBus Alert Response
Address on page 19.
Attempting to communicate with the EMC device over the SMBus with an invalid slave address, or invalid
protocol will result in no response, and the SMBus Slave Interface will return to the idle state.
SMSC EMC6D100/EMC6D101
Page 18
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
