C8051F120/1/2/3/4/5/6/7 C8051F130/1/2/3
Rev. 1.4
259
19. System Management Bus / I2C Bus (SMBus0)
The SMBus0 I/O interface is a two-wire, bi-directional serial bus. SMBus0 is compliant with the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus. Reads and writes to
the interface by the system controller are byte oriented with the SMBus0 interface autonomously con-
trolling the serial transfer of the data. A method of extending the clock-low duration is available to accom-
modate devices with different speed capabilities on the same bus.
SMBus0 may operate as a master and/or slave, and may function on a bus with multiple masters. SMBus0
provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic,
and START/STOP control and generation.
Figure 19.1. SMBus0 Block Diagram
SFR Bus
Data Path
Control
SFR Bus
Write to
SMB0DAT
SMBUS CONTROL LOGIC
Read
SMB0DAT
SMB0ADR
S
L
V
6
G
C
S
L
V
5
S
L
V
4
S
L
V
3
S
L
V
2
S
L
V
1
S
L
V
0
C
R
O
S
S
B
A
R
Clock Divide
Logic
SYSCLK
SMB0CR
C
R
7
C
R
6
C
R
5
C
R
4
C
R
3
C
R
2
C
R
1
C
R
0
SCL
FILTER
N
SDA
Control
0000000b
7 MSBs
8
A
B
A=B
8
0
1
2
3
4
5
6
7
SMB0DAT
8
SMB0CN
S
T
A
S
I
A
A
F
T
E
T
O
E
E
N
S
M
B
B
U
S
Y
S
T
O
SMB0STA
S
T
A
4
S
T
A
3
S
T
A
2
S
T
A
1
S
T
A
0
SCL
Control
Status Generation
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
IRQ Generation
S
T
A
5
S
T
A
6
S
T
A
7
A
B
A=B
SMBUS
IRQ
Interrupt
Request
Port I/O
1
0
SDA
FILTER
N
7
Summary of Contents for C8051F12 Series
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