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CHAPTER 13 SMB0 (SYSTEM MANAGEMENT BUS 0)
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13.4.9 Matching address detection method
In SMB mode, a particular slave device can be selected by transmitting that slave address from the master.
The detection of matching addresses is performed automatically by hardware. If a local address has been set in
SMB slave address register 0 (SMBSVA0), and the slave address sent from the master matches the address set in
SMBSVA0, or if the extension code is received, an INTSMB0 interrupt request is generated.
13.4.10 Error detection
In SMB mode, because the status of the serial data bus (SDA0) during transmission is also input to SMB shift
register 0 (SMB0), transmission errors can be detected by comparing the SMB0 data before transmission start and
at transmission end. If two data do not match, a transmission error is considered to have occurred.
13.4.11 Extension code
(1)
An extension code is considered to have been received when the high-order four bits of the receive address
are 0000 or 1111, and in this case the extension code receive flag (EXC0) is set and interrupt request
(INTSMB0) is generated at the falling edge of the 8th clock.
The local address stored in SMB slave address register 0 (SMBSVA0) is not affected.
(2)
When 111110
××
is set in SMBSVA0 and 111110
××
0 is transferred from the master during transfer of a 10-
bit address, the following occurs. However, INTSMB0 is generated at the falling edge of the 8th clock.
Matching high-order 4 bits: EXC0 = 1
Matching 7-bit data: COI0 = 1
Note
Note
Note
EXC0 : SMB status register 0 (SMBS0) bit 5
COI0 : SMB status register 0 (SMBS0) bit 4
(3) Because the processing after an interrupt request is generated differs depending on the data that follows
the extension code, it is performed by software. For instance, if operation as a slave is not desired following
the reception of an extension code, set LREL0 to 1, in which case the following communication standby
status is entered.
Table 13-3. Extension Code Bit Definition
Slave Address
R/W Bit
Description
0000 000
0
General call address
0000 000
1
Start byte
0000 001
×
CBUS address
0000 010
×
Address reserved for different bus format
1111 0
××
×
10-bit slave address specification
Addresses reserved for system management bus are described below.
Slave Address
Description
0001 000
SMB host
0001 100
Response address for SMB alert
1010 001
Default address of SMB device
1001 0
××
Free address