20.4 SMB0 Control Registers
20.4.1 SMB0CF: SMBus 0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
ENSMB
INH
BUSY
EXTHOLD
SMBTOE
SMBFTE
SMBCS
Access
RW
RW
R
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0x0
SFR Page = 0x0; SFR Address: 0xC1
Bit
Name
Reset
Access
Description
7
ENSMB
0
RW
SMBus Enable.
This bit enables the SMBus interface when set to 1. When enabled, the interface constantly monitors the SDA and SCL
pins.
6
INH
0
RW
SMBus Slave Inhibit.
When this bit is set to logic 1, the SMBus does not generate an interrupt when slave events occur. This effectively removes
the SMBus slave from the bus. Master Mode interrupts are not affected.
5
BUSY
0
R
SMBus Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It is cleared to logic 0 when a STOP or free-timeout is
sensed.
4
EXTHOLD 0
RW
SMBus Setup and Hold Time Extension Enable.
This bit controls the SDA setup and hold times.
Value
Name
Description
0
DISABLED
Disable SDA extended setup and hold times.
1
ENABLED
Enable SDA extended setup and hold times.
3
SMBTOE
0
RW
SMBus SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the SMBus forces Timer 3 to reload while SCL is high and
allows Timer 3 to count when SCL goes low. If Timer 3 is configured to Split Mode, only the High Byte of the timer is held in
reload while SCL is high. Timer 3 should be programmed to generate interrupts at 25 ms, and the Timer 3 interrupt service
routine should reset SMBus communication.
2
SMBFTE
0
RW
SMBus Free Timeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL and SDA remain high for more than 10 SMBus clock
source periods.
1:0
SMBCS
0x0
RW
SMBus Clock Source Selection.
This field selects the SMBus clock source, which is used to generate the SMBus bit rate. See the SMBus clock timing sec-
tion for additional details.
Value
Name
Description
0x0
TIMER0
Timer 0 Overflow.
0x1
TIMER1
Timer 1 Overflow.
0x2
TIMER2_HIGH
Timer 2 High Byte Overflow.
0x3
TIMER2_LOW
Timer 2 Low Byte Overflow.
EFM8SB2 Reference Manual
System Management Bus / I2C (SMB0)
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