BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
406
Section 14: Serial Configuration Interface
Document
1250_1125-UM100CB-R
If the device that is addressed is not an SMBus device, then it will most likely use a different protocol. In this
case a mapping will need to be done from the SMBus commands to those that the device supports. The Send
Byte and Receive byte commands perform the fundamental transfers, but in many cases the other commands
can be used (for example many memory devices can use the Read Word command to set the address pointer
and read back two bytes). Since it is not interpreted by the hardware the PEC byte can be used as an additional
byte in the transfer.
E
XTENDED
P
ROTOCOL
Send Byte (000)
Yes
No
No
Send a single byte to the slave.
Receive Byte (101)
No
No
Data
Read a single byte from the slave using a
simple read with no associated command.
Write Byte (001)
Yes
Data
No
Send a command byte and a single data byte
to the slave.
Read Byte (011)
Yes
Data
No
Send a command to the slave and read back
a byte.
Write Word (010)
Yes
LSB
MSB
Send a command and two bytes to the slave.
Read Word (100)
Yes
LSB
MSB
Send a command to the slave and read two
bytes.
EEPROM Read
(111)
Yes
LSB
MSB
Send a command and one byte to the slave
and read four bytes back. This matches a 32
bit read from a >16 kbit EEPROM.
Table 285: Supported SMBus Transfer Types
(Cont.)
Transfer Type
(smb_tt)
Command
(smb_cmd)
1st Byte
(smb_data[7:0])
2nd Byte
(smb_data[15:8]
Description
S Slave Address Wr
Command Code
P
1
7
1
1
8
1
1
A
A
S Slave Address Rd
A P
1
7
1
1
8
1
1
A
Data Byte
S Slave Address Wr
Command Code
Data Byte
P
1
7
1
1
8
1
8
1
1
A
A
A
S Slave Address Wr
Command Code
S Slave Address Rd
S Slave Address Wr
Command Code
A P
1
7
1
1
8
1
7
1
1
1
8
1
1
A
A
A
Data Byte
S Slave Address Wr
Command Code
Data Byte Low
P
1
7
1
1
8
1
8
1
1
1
Data Byte High
A
A
A
A
8
S Slave Address Wr
Command Code
S Slave Address Rd
A
S Slave Address Wr
Command Code
1
7
1
1
8
1
7
1
1
1
8
1
A P
8
1
1
. . .
A
A
A
Data Byte Low
Data Byte High
S Slave Address Wr
Command Code
Data Byte Low
1
7
1
1
8
1
8
1
. . .
S Slave Address Rd
A
1
7
1
1
8
1
Data Byte High A
1
A
A
A
Data Byte Low
A
A
P
8
1
1
Xtra Byte High A
1
Xtra Byte Low
. . .
8
8
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