C8051F300 Datasheet, PDF (109/176 Pages) List of Unclassifed Manufacturers – Mixed Signal ISP Flash MCU Family

C8051F300/1/2/3/4/5
13. SMBus
The SMBus I/O interface is a two-wire bidirectional serial bus. The SMBus 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 SMBus interface autonomously controlling
the serial transfer of the data. Data can be transferred at up to 1/10th of the system clock operating as
master or slave (this can be faster than allowed by the SMBus specification, depending on the system
clock used). A method of extending the clock-low duration is available to accommodate devices with differ-
ent speed capabilities on the same bus.
The SMBus interface may operate as a master and/or slave, and may function on a bus with multiple mas-
ters. The SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization,
arbitration logic, and START/STOP control and generation. Three SFRs are associated with the SMBus:
SMB0CF configures the SMBus; SMB0CN controls the status of the SMBus; and SMB0DAT is the data
register, used for both transmitting and receiving SMBus data and slave addresses.
SMB0CN
MT SSAAAS
AXT TCRC I
SMAO K B K
TO
RL
ED
QO
RE
S
T
SMB0CF
E I BESSSS
N N U XMMMM
SHS T B B B B
M YHT FCC
B
OOT S S
LEE1 0
D
Interrupt
Request
SMBUS CONTROL LOGIC
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
SDA Control
IRQ Generation
Data Path
Control
SMB0DAT
76543210
00
T0 Overflow
01
T1 Overflow
10
TMR2H Overflow
11
TMR2L Overflow
SCL
FILTER
SCL
Control
SDA
Control
N
C
R
O
S
S
B
A
R
FILTER
SDA
Port I/O
N
Figure 13.1. SMBus Block Diagram
Rev. 2.8
109