14 I
2
C (I2C)
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
14-17
TECHNICAL MANUAL (Rev. 1.0)
(2) STOP condition interrupt
Master mode
SDA
SCL
(BRT + 3)
×
3
f
CLK_I2Cn
TXSTOP = 0
STOPIF = 1
TXSTOP = 1
RXD[7:0] read (during reception)
Slave mode
SDA
SCL
BSY = 0
STOPIF = 1
(f
CLK_I2Cn
: I2C operating clock frequency [Hz], BRT: I2CnBR.BRT[6:0] bits setting value (1 to 127))
Figure 14.5.1 START/STOP Condition Interrupt Timings
14.6 Control Registers
I2C Ch.
n
Clock Control Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
I2CnCLK
15–9 –
0x00
–
R
–
8
DBRUN
0
H0
R/W
7–6 –
0x0
–
R
5–4 CLKDIV[1:0]
0x0
H0
R/W
3–2 –
0
–
R
1–0 CLKSRC[1:0]
0x0
H0
R/W
Bits 15–9 Reserved
Bit 8
DBRUN
This bit sets whether the I2C operating clock is supplied in DEBUG mode or not.
1 (R/W): Clock supplied in DEBUG mode
0 (R/W): No clock supplied in DEBUG mode
Bits 7–6
Reserved
Bits 5–4
CLKDIV[1:0]
These bits select the division ratio of the I2C operating clock.
Bits 3–2
Reserved
Bits 1–0
CLKSRC[1:0]
These bits select the clock source of the I2C.
Table 14.6.1 Clock Source and Division Ratio Settings
I2CnCLK.
CLKDIV[1:0] bits
I2CnCLK.CLKSRC[1:0] bits
0x0
0x1
0x2
0x3
IOSC
OSC1
OSC3
EXOSC
0x3
1/8
1/1
1/8
1/1
0x2
1/4
1/4
0x1
1/2
1/2
0x0
1/1
1/1
(Note) The oscillation circuits/external input that are not supported in this IC cannot be
selected as the clock source.
Note: The I2CnCLK register settings can be altered only when the I2CnCTL.MODEN bit = 0.