The debounce time of the I
2
C interface uses the system clock to in effect add a debounce time to the
external clock to reduce the possibility of glitches on the clock line causing erroneous operation. The
debounce time, is 2 system clocks. To achieve the required I
2
C data transfer speed, there exists a
relationship between the system clock, f
SYS
, and the I
2
C debounce time. For either the I
2
C Standard or
Fast mode operation, users must take care of the selected system clock frequency and the configured
debounce time to match the criterion shown in the following table.
I
2
C Debounce Time Selection
I
2
C Standard Mode (100kHz)
I
2
C Fast Mode (400kHz)
2 system clock debounce
f
SYS
> 4MHz
f
SYS
> 10MHz
I
2
C Minimum f
SYS
Frequency
I
2
C Registers
There are four control registers associated with the I
2
C bus, SIMC0, SIMC1, SIMA and I2CTOC and
one data register, SIMD. The SIMD register, which is shown in the above SPI section, is used to store
the data being transmitted and received on the I
2
C bus. Before the microcontroller writes data to the I
2
C
bus, the actual data to be transmitted must be placed in the SIMD register. After the data is received
from the I
2
C bus, the microcontroller can read it from the SIMD register. Any transmission or
reception of data from the I
2
C bus must be made via the SIMD register. The SIM pins are pin shared
with other I/O pins and must be selected using the SIMEN bit in the SIMC0 register.
Note that the SIMA register also has the name SIMC2 which is used by the SPI function. Bit SIMEN and
bits SIM2~SIM0 in register SIMC0 are used by the I
2
C interface.
Register
Name
Bit
7
6
5
4
3
2
1
0
SIMC0
SIM2
SIM1
SIM0
¾
¾
¾
SIMEN
¾
SIMC1
HCF
HAAS
HBB
HTX
TXAK
SRW
IAMWU
RXAK
SIMD
D7
D6
D5
D4
D3
D2
D1
D0
SIMA
IICA6
IICA5
IICA4
IICA3
IICA2
IICA1
IICA0
D0
I2CTOC
I2CTOEN
I2CTOF
I2CTOS5
I2CTOS4
I2CTOS3
I2CTOS2
I2CTOS1
I2CTOS0
I
2
C Register List
Rev. 1.50
88
April 28, 2020
BS83B08-3/B12-3/B16-3/B16G-3/C24-3
8-Bit Touch Key Flash MCU
S T A R T s i g n a l
f r o m M a s t e r
S e n d s l a v e a d d r e s s
a n d R / W b i t f r o m M a s t e r
A c k n o w l e d g e
f r o m s l a v e
S e n d d a t a b y t e
f r o m M a s t e r
A c k n o w l e d g e
f r o m s l a v e
S T O P s i g n a l
f r o m M a s t e r